OK, managed to epoxy on a few "T" nuts to the bottom piece which will attach the petcock valves. I've positioned them with a few jigs I cut from some old fiberglass layup done on a previous project; just cut some holes the correct distance apart to fit the petcock valves. Once this glue sets, I'll lay down a slurry of epoxy and milled glass fibers to really solidify the assembly. I actually would have done this all in one step but ran out of the milled fibers to make the reinforcement with. Figure it's okay to "tack" the nuts down right now and then reinforce them later.