[Zeke]

Looks good so far, the flaps are a good idea. You can use epoxy on the underside and in between the back of the flare and the metal if you want, but body filler (bondo) will work better over regular polyester resin. Lay your mat and/or cloth with resin on the outside seam of the flare and grind to shape when hard. Finsh with body filler and prime.

Another thing about epoxy is that it cures with heat whereas resin can be made to cure in cold temps with additional catalyst.