to sum it up (i have opemus 5 and some el nikkors) - 5.6/80 will work fine with every types of lensboards on Op5
for bigger 35mm film lens (say 4/40, 2.8/50, 2.8/63) you need another lensboard made by meopta - it's not so shallow but it has nearly 52mm internal diameter (and 39mm thread) so these bigger lens will fit inside. try to contact some meopta dealers....
with my friend we had the same problem (with the same lens) and solved it this way (but we're from czech republic, so meopta is, so it was easy to obtain it from second hand store for $2).