I bought a proper ss hook to tow a tube, but I'm not familiar with fibreglass and I dont know if it's strong enough just top attach to the fibreglass or if i should get a piece of plywood or 2x4?
Yep, need a backing plate of some sort. The fibreglass is not strong enough for a ski eye or cleat etc... Mount it through the backing plate. Do not simply screw it in.
Bandit, You will need to bolt it to the boat with some sort of backing plate. I would use solid pressure treated 1X4 or some SS, Aluminum or brass plate of say 4X4X3/16"
You will need a backing plate. It can be stainless steel, aluminum or wood. But you want it to spread the forces out over a wider area than just a nut and washer. Here's a link to the installation I did on my 2005 Trophy 2052. Of course this is a recessed hook but the idea is the same with the backing plate.
