Ok - Fantastic. Thanks everyone for the advice.

I'll use the blind nuts i've already epoxied in, but i'll use some spring washers under them for added security.

I'll wait to drill the engine mount holes, and when I do i'll use a bolt with a spring washer, and a nylock nut on the other end. I'll just CA the engine on while i am building, and then remove the mounts and drill the holes on the drill press at work once i have the wing on, and some idea of balance.

Also, when drilling the holes in the mounts, do i just use an everyday punch that you use in metal work to make a little dint, then drill the holes on the drill press? I have never worked with 'glass filled' mounts before!

As for needle valve placement, I assume I just make sure it protrudes somewhere outside the balsa cowl for adjustments - it doesn't matter if it is horizontal or vertical?

Thanks everyone!