Just my 2 cents, but I would not paint the firewall before installation, because I think you will possibly get a stronger and better adherance if the glue joint for the firewall joins a more porous non-painted surface. It may not matter, (especially iof you've already done it). I usually polyurethane the firewall and engine compartment later.

Regarding the hatches, I have some photos of the double hatch area on the prototype. As I said earlier, Kevin had two hatches as well, but devised a method where he only uses one screw for BOTH hatches. (Make sure that one is tightened down well).