Yes, I used 3m filler with Fiberglass strands in it (sure it has a better name may be duraglass) and I filled the front and back sides of the holes to ensure it will last. Then with glaze putty, I added a light skim coat over all the holes on the face of the fairing to finish it off. Came out real nice.
Polyester resin (bondo, fiberglass, duraglass etc.) and fairing plastic will fall apart when used to fill holes or repair cracks. Sure, it doesnt happen right away but it will. The best product to repair plastic with is JB Weld. Tried and true in my shop hundreds of times. Because it is a epoxy base its shrink rates are much slower. Polyester resin moves a lot.