Wyatt,
Sounds like you do not need to have access to this area much, if at all. I would suggest the following.... locate the same area on the good hull, and use masking tape to mask off an area a couple inches bigger than the hole in the other hull. Wax the tape and lay-up 6-8 layers of glass and resin on the waxed tape.... allow to cure and remove. Cut the new glass to a diameter about 1/2" bigger than the existing hole. Sand and paint the new piece of glass to match the color of the hull. Remove the old inspection port entirely... place the new round glass piece over the top of the old hole and mask carefully around with tape. Lightly sand the 1/2" between the tape and the hole... lightly sand the glass cap around the bottom 1/2". Use 3M 4200 fast cure marine adhesive to glue the new glass cap in place. clean up the excess 4200 around the perimeter with mineral sprits and when happy with the clean up, remove the tape immediately... allow the 4200 to cure for a couple days before use. This will seal the hole and allow you to have access in the future by cutting the 4200 out from under the glass cap with a razor knife and some carefully applied heat.

good luck,
nacrazc