Stick the smaller power pack (MB21?) on the body and you don't have to worry about the curve at the bottom - makes for a smaller package to lug around, too. I do fully agree, for 35mm macro work, IMHO you simply cannot do any better than the F4 (macro work is somewhat my specialty) The PB-6 works fine on an F4. You might like this combo - a 300mm with a nikon 6T lens mounted on front (no, the step down rings don't create any vignetting) - add to that about 25mm extension, and you're shooting life-size - but from about 3 feet!