Hi Will,
Jim Boyer's method to repairing holes in timber mozzies goes like this:
1. take an angle grinder to it and bevel the edge of the hole to about a centimeter or more all around.
2. wet the bevelled edge with resin.
3. lay fibreglass tape over the hole and on the bevelled edge, as much of the bevelled edge as possible.
4. brush resin over the tape.
5. fill the hole with a fibre glass filler - he recommends the west system of "microfibre blen gap filler (403)". This is mixed into the fibre glass resin till it is of a consistency desired, and then used to fill the hole.
6. leave a bit too much and sand it down later.
I have used this method and am really pleased with the results.
Jim says it is stronger than the original ply.
Hope it goes well.
Keith