I have the F4s (and the F2 and F3) and would prefer the version with the smaller battery holder, F4 without s.
I waw yesterday on the flea market and one gay had an F, F4s, F5 (and a lot of other gear, RB67, Mamiya 23, plate cameras, etc.) unfortunately at delusory prices.
I looked trough both the F4 and the F5 and it seemed to me the F5 has a much bigger viewer.
Unfortunately both had different focal lenses on them and the one from the F4 could not be removed. This means I couldn't really judge it, but the viewer of the F5 looked definitevily bigger to me.
Can somebody with both the F4 and F5 confirm (or infirm) this?