The robart drill guide is self adjusting. Mark the location of both the wing and aileron, 4" apart, use a 90 degree guide(i use the thing my sander came with to offset a specific angle) Place this on the bottom of the wing with the guide at 90 degree or perpendicular, at the mark already made, and make a mark up and down on the facing. Do this for all marks on both wing and ail facing.

Take the drill guide($5 or so) and drill where the mark made can be seen through the drill guide. Don't drill deep though. let the hinge point make some of the indent into the foam.

This system is almost foolproof. Again, I've had a number of giant scale without any problems.

The secret is using the syringe to force the epoxy or glue into the hole. Trying to drip the glue in with a toothpick or similar results in a very poor bond. By using the syringe, you also spread the glue on the inside of the surface, making the actual bonding area bigger than without.

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Did I mention, buy the drill guide from Robart, this is indespensible to this working well!!!!