Regehr,
I'm still finishing up the mounting. I bought these rails
http://www.iboats.com/Deck-Mount-7005-D-72-length-Westland/dm/*******.193869343--**********.252575803--view_id.117997
from iboats, so that I can mount the bimini and solid rear brace to the same rails, so that I can adjust the position fore and aft a foot or so each way, and so that I can fold the bimini and slide it back to rest on the stern when I'm trailering. I haven't finished the mounting yet, just a temporary mounting with double stick tape. I intend to screw through the slide track and through the topside mounting surface, and into a plywood mounting block inside the hull. It is also OK, just not quite as secure, to screw directly to the mounting surface of the hull. I wouldn't use epoxy or 5200 to seal those screws, at most use 3M 4200, or Boatlife Boatcaulk on the screws, so that if you want to remove them at some time, you will be able to without drilling them out.