For filling the holes instead of using the PC product use an epoxy putty stick. They are somewhat like a Tootsie Roll candy in that there is an inside core and wrapped around it is the second half of the epoxy mix. You cut off a slice then knead the slice to mix it. Rather than being a thin mix that is difficult to get into the hole you just push in the piece of putty with your finger until the hole is filled. It hardens very quickly so within an hour or so you can reinstall the hinge. The remainder of the stick keeps well if you wrap it back up and put a piece of tape over the exposed end. For hole filling you only need to take a small slice off the stick.
I usually by the epoxy putty sticks made for wood repair, it works great on
fiberglass too. The advantage to it is the color is beige and the texture is smoother than some of the epoxy putty sticks made for metal repair. It is also great for repairing dings in the
fiberglass shells. But you do want to trim any overfill off before it hardens as it get very hard to sand once it has cured.