As you mentioned, the handle of the Mora does make it bulge a bit on the back but I haven't noticed any discomfort as a result of that. I can't immediately think of a way around that. On my other sheaths I didn't have that issue because I could secure them by their guards, but this version of a mora doesn't have one so in order to secure it well the sheath had to be much longer.
@mikeyelefant it's the 4 1/4" blade. If I had to do it over again I would probably get the shorter blade as it's slighly better for light bushcrafting uses.