By using a syringe for epoxy, or another form of expanding glue(gorilla type) the glue sets up around the hinge point the the bevels. Also making sure your facing is 1/4" helps vs 1/8". When using CA hinges with foam wings, the CA actually eats away the foam on the inside of the wing and the CA hinge is attached only to the facing. Look at a crashed plane with foam and these type of hinges. Unless you use odorless, but a lot of times odorless is not as thin and won't wick well so the hinge still isn't attached as well.

As far as making the hole a little bigger, if there is a bevel(leading edge of rudder) I use the dremmell to hog it out a bit, if the surface is flat(trailing edge of the vertical post) I insert the hinge and swivel it 360 degrees while applying a small amount of presure to the balsa, and the larger portion of the hinge makes the hole the correct size.

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