Thanks Hermes, I honestly hadn't really considered barrel lenses, but I could get a sinar shutter and that could be a great option. Barrel lens seem generally cheaper. My only concern is do you know if there are multicoated process/barrel lenses? I really don't know much about them. I try to stick with modern multicoated lenses as I shoot color and like to enlarge as much as possible, but maybe with a very capable lens shade (like the sinar bellows mask 2) I probably wouldn't notice any difference?

That's an interesting point Drew. I have a 6x9 roll back that I never use....it would at least help me confirm that a 600mm would be useful for me. I prefer to shoot the biggest (up to 8x10) neg that I can, but this could be a good solution for certain shots.

You mention Drew, that telephoto lenses might not provide the optical results of normally designed lenses. I always figured once you get to about 600mm teles would be a great benefit as they would require less bellow draw and thus greater stability and improved performance, but if they are not as sharp to begin with maybe this is canceled out? Or not? I guess I have a lot to learn about giant lenses.......I seriously thought that I was crazy for wanting a 450mm....and now I think im even crazier for wanting something longer, but it seems to keep coming up.

I guess in a perfect world I would just drop 10 grand and pick up the new Schneider apo-tele-xenar 600/800 and a Fine art XXL 1100......but of course that is not even close to the realm of possibility at this point.