After spending many hours laying things out (Measuring, looking at it from every angle, checking what's behind the feet, etc) I finally drilled my holes last night.
The fiberglass on the starboard side was 1/2" thick at each hole (Hooray for MasterCraft). The port side was 3/8" at the front hole and 7/16" at the rear hole.
So, I'm well over the 1/4" minimum but I still plan to cut some plastic reinforcements, bend them with a heat gun to conform to the inside of the hull and then fiberglass them in place.
I ended up having to grind the front to feet to conform to a ridge in the hull because there was no flat place to bolt it wide enough for the foot. That was scary at first but came out really well. I used a contour gauge like you'd use for crown molding to mirror the shape of the hull at that point then took it to the garage. I started with an angle grinder and a sanding disk and then moved to a 1" diameter sanding drum on the drill press for the final "tuning".