RE: Ironing on Balsa sheeting
I've used this technique with Titebond and 3/32" sheeting over foam and it worked well. The retired wing has survived many years in a hot attic without de-laminating, so I assume the bond is as permanent as anything can be in model aviation.
I used a household iron rather than my covering iron in order to heat a larger area at one time.
Be sure to do your work with the core supported by the foam shucks because it's very easy to iron in a warp otherwise.