Replacing a blind nut in the firewall can be a royal pain...


If you can run a straight wire back into the wing opening from the bolt hole... you put a 90 deg bend in wire that JUST fits inside the screw threads. put the blind nut n the wire so the flat is to the bend... run it through the hole fromthe back (may need another wire and heat-shrink tube or tape to guide it in some cases) and pull the blind nut firmly into the firewall. (now get the wire out without knocking the nut free again...)

You can also use threaded rod... similar trick, but if you put vaseline on the rod... you can put some 30 min epoxy on the blind nut and tighten it in place till the epoxy cures.

If you've got some mild curves to negotiotiate... nyrod and a piece of 2-56 threded rod (the 2 inch pisece you get for a pushrod end) put a 2-56 nut between the blind nut and the nyrod... push the nut in place. Again vaseline can allow use of epoxy to hold the nut firmly. (you can use washers and another nut to pull the blind nut firmly into the plywood.)

From there... its all variations on a theme.. when REALLY desperate... you can file the head off of a correct size screw... file flats on opposing sides and drill for fishing line to pull the thing in with. (and that's also how you make a 4-40 threarded end for scale rigging....)