It sits just on the edge of one of those pcv chambers underside of cover so yep it can be patched from the inside and ground down to flush from top.
I've been using carbon steel wire brushes and mini sanding drums in my dremel to clean up the ports, followed with various grades of wet-n-dry. However with the cam cover i was using cutting burrs which remove material pretty quickly...especially soft alloy.
I half regret pulling the head back down instead of bolting it onto the freshly cleaned block deck, but then i wouldnt have found that large chunk of wire brush bristles (?) under a spring retainer and the single p1 (hydrolic) retainer/collets used on a single valve. Not complaining though, the extra stuff ol'mate did to the head makes up for it.
I'm pretty sure using non matching retainers is not the best.