I just used the backing board that came with the mount. 1/2 inch plywood, about twice as large as mount plate itself. It then has four bolts that go through the mount plate, the
fiberglass, a washer, then the nut. It sandwiches the fiberglass quite securely. I also figured that by placing it in the 45 degree section, the fiberglass would have the additional strength and rigidity of the angles close on either side of the mount. I guess time will tell.
I also plan to keep the table top smaller than what they deem the max, so that will contribute to less stress than the design can hold.
These are marketed for mounting in boats, particularly onto fiberglass benches, as advertised, so I assume they are engineered for the same. Seems quite secure. I did see one install video, where the owner glassed in some wooden stiffeners on the inside of his bench, but this was for an install in the center of a relatively long bench with no other support.
Perhaps I will consider screwing a base plate onto the floor, then adding one or two wood triangle braces (or block) between the floor base plate and the Lagun backing plate, gluing these all together. Will think about it while doing the rest. Perhaps overkill, but probably worth it.
As one YouTube vlogger that I follow states, "This is polishing the diamond", getting critical input then modifying your approach.
Comments?