personally i would run a file over the housing or put some grinding paste on a sheet of glass and make sure its flat and then use an instant gasket or silicone
I wish i knew something about KR's so i was like knowledgeable about them and everything like what you lot are
None of the ones I have are flat, I use Loctite 515 or 518 and I have never had one leak.
I do not use silicone sealant, only the anaerobic stuff (like 515 or 518). It only sets when you exclude the air so you do not end up with those long strings of sealer in your engine or dangling off the sides.