If my CB trunk was glassed over, it would just be a matter of cutting out the slot. Chances are the "repair" would not be gel coated, so sanding off the bottom paint would probably show you the area that was glassed. Cut the middle and do exploratory surgery from there to find the extent of the trunk.
I've got an Irwin 28 with an intact, although leaky, CB system. I'm going to drop the board on Thursday to have at the leak and I was planning on patterning it while I have it out. If you wind up with a sister ship, let me know and I'll make you a copy of the CB pattern. Could provide some photos and dimensions of the trunk and hardware too if needed.
I've got an Irwin 28 with an intact, although leaky, CB system. I'm going to drop the board on Thursday to have at the leak and I was planning on patterning it while I have it out. If you wind up with a sister ship, let me know and I'll make you a copy of the CB pattern. Could provide some photos and dimensions of the trunk and hardware too if needed.