We have two K31s - both with the Swiss Products aluminum clamp-on scope mounts, and UTG (I think?) integrated ring & base setup.
One rifle has a Bushnell 10x40 mil dot - wasn't planned that way, but ended up there after doing some other scope swaps. My eyes don't mind it one bit!
The other currently wears a Scorpion 3-9x40. My son figures this works OK for him so it will stay there for a while.
Both scopes have bikini covers that will just clear the rear sights but the Bushnell is very close. With this setup a larger objective would not fit.
Good luck - you will enjoy having optics on your Swiss!
Kermode