On smaller planes, you often have to check larger carry ons at the gate because they will not fit overhead and you are prohibited from holding them on your lap.
A carry on size Pelican (1510?) is the way to go. Gear is safe even if checked as baggage but meets carry on requirements. It is also dust proof and waterproof.
8x10 with reducing back is the way to go realizing that bellows compression might limit 4x5 wide angle work.
Depending on where you are going, you might consider shipping your gear, or some of it, UPS.
I carry on the Pelican and the put a Photobackpacker backpack (filled with clothes, etc.) inside a suitcase and carry the film in a "purse" style bag (LL Bean zipped beach tote).
I travel routinely with a 4x5 Technika (or occasionally the larger Technikardan) in a Lowepro Flipside 400AW backpack. It holds the camera with one lens mounted, around ten film holders, 4-5 relatively large extra lenses and some accessories. I usually carry my film boxes (usually 6 boxes of Portra 160 re-packed with 50 sheets per box) as well as my travel documents in my 'personal item', a very small messenger bag from Manhattan Portage (smaller than a laptop bag, it's really a man-purse I guess). I've had no problems flying internationally this way, I try to fly Lufthansa when I can but I've also recently flown on Continental, United and some others I can't think of at the moment.
I check a Zero Halliburton suitcase which contains my tripod, a few extra (empty) film holders, a backup lens or two and my clothes.
I don't see any reasonable way to carry on all of the gear you're talking about, especially since you'll have to carry your film boxes on as well, you can't check them. If you insist on taking the gear you mention, make sure you have equipment insurance and check the 8x10 in a pelican case. You could probably carry-on the 4x5 gear and all of your film.
I suppose if you're traveling with a companion and you could split the load, things may be different, but if you're alone you'll have problems conforming to the size and weight limits.
If I had to travel with an 8x10 camera, there is no doubt in my mind that I'd shoot with an arca-swiss. It's small, rigid and reliable. It's an even better kit if you absolutely need to carry two formats, since a lot of the parts are interchangeable. But frankly I don't see the point in traveling with two formats these days with all of the tight airline restrictions. You'll be duplicating a lot of gear (holders, some lenses, lots of film boxes, etc.) If you decided to shoot all 8x10 then perhaps you could fit your camera, lenses and film into a carry-on bag. Carrying an 8x10 camera and a reducing back would be an ok compromise I guess, but I don't really get it. If you plan to shoot mostly 8x10 and a few 4x5 pics, why not just stick with 8x10? And if you plan to shoot mostly 4x5, then it's inefficient to carry a large 8x10 camera.
If you go with 8x10 you'll probably have to check your film holders which stinks since you'll be unable to shoot if your luggage gets lost. But I don't see any way around that. Shooting 4x5 lets you carry all of your really critical gear on the plane. The only exception is the tripod, but you could probably find a tripod most places in the world in an emergency.
If you want to really get the most out of a regulation-sized bag, I would suggest one of the Think Tank bags. Some of them are sized specifically to the USA or International carry-on standards and they'll hold quite a lot. Better still, you could go with an aluminum case like a Zero Halliburton or Rimowa. Both make IATA sized carry on cases and because they're aluminum the walls are thin and you can really maximize space inside the bag, though you'd still probably want to add padding of some sort. I don't see the point in making a custom bag since there are plenty of manufacturers who already make bags specifically designed to get the most out of a regulation-sized carry-on bag.
Have you considered just sticking to 4x5 but buying a wooden 4x5 that's pretty like your Deardorff? That would make your travels a breeze.
Don't let all of this dissuade you. I love traveling with 4x5 despite the hassles and the results are very rewarding.
I try to book my seats towards the rear of the plane. That often means I can board early and it ensures there is space left in the overhead bins. But the great thing about my small 4x5 kit is that the Flipside 400 backpack will even fit under most seats if absolutely necessary, though it would leave me with no legroom.
Lately they've been loading my planes from the front, so getting good overhead placement means the lower numbered seats.
I used to use the Pelican 1510 until it cracked the hinge and latch on me. The other latch held it from opening but I am no longer a fan, also because of their empty weight.
Right now I use a Think Tank Airport Antidote for a compact 4x5 kit. It is well below the airline regs and I can even slip it under the seat in front of me, so I never have needed to gate check it. I dread the thought of having anything larger to be honest, it is still a serious lump to lug around.
If I were traveling with 8x10 and wanted to really get serious work done, I would invest in a custom Strebor or find a Lightware or Tenba Air case that fits all of my 8x10 gear, including a bag for holders, tripod head, changing tent, etc. Then I would ante up to pay excess baggage or ship it on ahead via FedEx and do it right. Insured of course. None of this is cheap and it means it is usually better to drive if it is within a reasonable driving distance.
Maybe you can get a Dorf into a carry-on but you'll always be leaving something behind or compromising in some way. And you didn't get into 8x10 to compromise did you?
I'd also be mean and brutalistic and use a system monorail like a Sinar/Arca/Linhof/Cambo/Toyo and have a solid camera with full movements once I decide to check or ship it. But the wood ones do make better pictures, lol.
I think the Arca Swiss F line is a beautiful camera also. No, it doesn't look like a piece of antique furniture like the Dorff but it looks great in it's own way.
I bust splinters off to clean my teeth ;-p
Air travel with film is my worry.
Last year TSA discovered a 50 sheet box of 4x5 Tri-X in my camera bag. They decided to open the box. they took it away for some time and returned it to me with some tape holding the box closed . . .OK.
When I went to load the film, I found that they had opened both inner pouches too. I loaded and shot two sheets. Later on I found that each sheet was either totally black or only half black!
What can be done? Ship film ahead, buy it locally, don't fly.
PS: I have a Kodak 2-D and understand. We are going on a family vacation this summer and the 2-D is staying home. My 4x5 is a lovely little Zone VI.
There's "air travel" and there's "air travel." It sounds like you're going to be flying all over the place and likely won't always be on airlines with the same rules about carry-on luggage and the same size airplanes. If that's the case and you really really don't want to check your gear even on a small airplane I wouldn't carry any LF gear, I'd bring a medium format system or a good digital camera. I'd be even more certain to do that if I was going to be doing a lot of hiking as you say you will be.
But if you feel you absolutely must use LF gear to accomplish what you want to accomplish, and absolutely must be able to use both 4x5 and 8x10 film, then I think you're on the right track with your last post in which you say you're leaning towards an 8x10 with a 4x5 reducing back.
Before you criticize someone, walk a mile in their shoes. That way when you do criticize them you'll be
a mile away and you'll have their shoes.