I'm currently using an 8.5-pound field camera (8x10) and I have some heavy lenses, between 2 and 4.5 pounds.
I've been trying to find the smallest (thinnest tube) and lightest tripod that can be reliably used with my 8x10 for when I take my gear on a walk or bicycle ride.
With the input of one of our forum members here, I've enlisted the services of the FLM factory to make a new tripod - in very small quantities at first.
This will test if it's a viable solution not just for our purposes, but if it could be an ultralight solution for any photographer.

The new tripod is the CP22-M2.
This means that the carbon tubes are 22mm in diameter, and it's a 2-section tripod.
The CP22-M2 will be 55.12" tall when fully extended, and 33.85" tall when folded.

While I wait for the new tripod, I've been doing my testing with the CP22-S4, which also uses 22mm tubes at the top, but is a 4-section tripod. I use a 38mm ball head with the tripod for my testing.
The 4-section should be slightly less stable overall than a 2-section, but that remains to be seen given that each leg section is longer on the M2.
Still, if a lot of the vibration comes from those skinny leg sections at the bottom of the tripod, then this could prove a winner.
The 2-section will certainly be easier to open and close quickly.

Nonetheless, I've had good success thus far with my 8x10 and regular-sized lenses (210 Plasmat, 300mm Tessar), and it's been successful with a Fuji GX680 system as well.
So I look forward to trying the new 2-section ultralight.

Price will be $299.00 USD, including shipping to US and Canada. Contact me and I'll send you some images of it next week when it comes in.
Thanks