I use a 75mm on 35mm quite a bit. It is a natural if you have a Bonica ETR series as the 75mm is the "normal" lens for the 645 format and then you just slap on the 35mm back. I also find the 75mm lens with 35mm to be a very good all around combo when I do not want to travel heavy.
I've got a Tamron 28-75 for my Nikon N80 that is very sharp and not much bigger than a prime lens. It doesn't have an aperture ring so it can only be used with a later af body. It's my event lens, I can go from portrait to group shot without changing lens. Auto-focus is a little slow, but for groups and portraits I don't need speed. Too slow for grandkids.