If you decide on the hidden hinge method check out this builder. Best explaination with pics to follow along with.
http://www.rvplane.com/?categoryid=3&dayid=567
for those 4-40 weld nuts, did you eyeball their location when you glued them in place? Or did you put glue on them and then install with the screws? That sounds like it would be a bit tricky because you can't get in there to hold all of them in place to start the threads. But I like the solution. Nut plates are a lot more work and yours is still removable.
Two questions:
1. Ron, why the wish for hinges?
2. For those putting a magnetometer in the tip, how are you securing the tip, or is the steel in the nut plates and hinge pins inconsequential?
Tom.