Shouldn't make a difference. I have the 4x5 tubes and have had great results with the amount of developer recommended by the manufacturer (can't remember the amount off the top of my head). I'd assume that's the minimum amount of developer needed to process the film normally, as tested by the manufacturer. Obviously this is one-shot developing only.
I haven't had any issues with uneven developing and it's been a heck of a lot easier than open tanks and hangers.
[QUOTE="jimjm,
(snip)
I haven't had any issues with uneven developing and it's been a heck of a lot easier than open tanks and hangers.[/QUOTE]
Since I 'invested' in BTZS tubes some 15 years (or so) ago, for both my 4x5 and 8x10" film, it will be a cold day in 'You-Know-Where' before I ever go back to either tray or 'hangers in tank' for developing any of my sheet film.