I used this trick to mount a battery switch to the underside of the back deck, just starboard of the rear hatch. Create a plate from a cutting board that works well. This plate is what you will use to screw your item onto. If you are able to mark out where the screw holes need to be, you can use threaded anchors on the backside of the plate. With the plate prepared, locate a relatively flat area where you can put the plate on to. Using a product similar to “Goop,” you can fasten the plate into position. Once the bonding agent has dried (overnight), test the plate to verify a solid adhesion to the fiberglass. I am always amazed at how strong the hold is. And because the “Goop” has some flex, it holds well. It can be removed bit by bit, and it leaves no trace behind. Well, now that the plate is stuck onto the boat, you can screw the device onto the plate. I fastened my little tool holder onto the side of the console this way a few seasons ago.
Hope this gives you another way to fasten components without damaging the boat.
.
