Any thoughts on how to mount a rigid seat while minimizing the potential for damage to the hull?

If you are paddling with leg drive, there's a surprising amount of force applied to the seat and seat back or backband.
A very common problem with commercial glass boats in my area (Vancouver Island) is getting small (a few mm) pebbles trapped between the seat and the hull. Small seat movements then grind a small hole through the hull. It is surprising how quickly the cockpit can take on water from a 'pinhole' size opening !
The problem is caused by a combination of:
-small gap between the seat and hull
-semi-flexible attachment of the seat to the hull (hanging from the coaming or attached to risers) which allows a bit of movement with each paddle stroke.

I've helped a couple of friends to repair holes under the seat of their kayaks. Often the seats aren't easy to remove.

With a wood core boat, it would take a lot longer to grind through the hull, but you still don't want the glass/epoxy coating to be penetrated.

I make rigid seats from epoxy/carbon/glass and mount them to 'side rails' bonded to the hull, and bond the seat to the hull as well. This is a direct copy of the NDK (Romany and others) seat style, though I make the seat back higher and don't use a backband. Those seats don't move.
Some ideas at:
http://www.paddlinglight.com/articles/how-to-install-a-ndk-kayaks-high-performance-seat/

Foam between the seat and the hull can help to keep out pebbles.

Keeping removal in mind might be a good idea, though you can remove anything with a 24 grit grinding disk!

Don't make your seat too thick - every cm separating your backside from the hull will change the stability feel of the boat.