Concur with all the above suggestions Bruce. My 4x5 is a 1940's era Graphic view I monorail with 16" amximum extension. With a 90mm lens. its is all scrunched up with just enough movement left for focusing. On the other end, with a 210 mm and trying for 1:1, its extended to the max. Looks like Steve has a pretty good thumbrule for bellows length.