after going to 600 grit wet sanding, this plug's ready for some parting wax. I'll get a few more on there before doing a layup of the mold.
That nubbin on the top will be where the gas cap goes. Looks kind of clunky but i could hardly give a shit right now.
I made it by forming a ring out of glass on this cylinder I made out of paper wrapped in packing tape:
Then attached the ring to a layup for the top like below; you can see the fuel cap in the background there; it's a nicely machined vented unit i got from a home-built aircraft supplier