Never heard of epoxying seats to a hull. Over time you may need to move them or adjust for length. How are you going to do that if epoxied?
I don't understand the concern about swinging. Most of my boats have hung seats and with two points of attatchment on each side the seat does not move.
I don't know if you are building a wooden stripper boat which seems most likely.
Kayak Motor Kit
The Moose Rack