Quote Originally Posted by LJH View Post
Regardless of which back, you'll be limited by the mechanical vignetting of the 4x5 orifice.

As such, you'll be limited to approx 90mm to 150mm focal lengths. This, of course, is pursuant on bellows' flexibility/compression on the shorter end.
For 150mm lens that is a 2.5 inch extension and only usable at infinity.