First, Drill a #40 hole where the center of the nutplate will be and cleco the nutplate in place on the surface. Use the nutplate as a guide to drill the mounting holes.
Now remove the clecos and feed both ends of the dental floss into the nutplate mounting holes which have been drilled into the surface.
With a long piece of tie wire fish out both ends of the dental floss.
Once you have fished out both ends run them through the nutplate mounting holes and tie the ends together. Be sure to orient the nutplate so when pulled into place it sits properly on the surface.
Pulling the dental floss snug the nutplate to the inside surface and insert a cleco in the center hole to hold it in place. Before doing this remember to enlarge the center hole to the proper diameter for the fastener planned.
Now remove the dental floss, install a second cleco in one of the outer mounting holes, remove the center cleco and install a pulled rivet.
Remove the last cleco and install the second pulled rivet.
Congratulations, you have installed an nutplate in a place you can't possibly reach...very handy.