You can seal the seams with epoxy and an acid brush. A good idea to go over them first with a covering iron. A heat gun or a hair dryer can be played on the open bays to tighten them up. Bubbles in the covering over wood can be punctured with a pin and then ironed down.
I have a Brodak P40 ARF and the instructions called for an iron, if I recall, and maybe even a heat gun. My thoughts are, if you are going to buy ARF's, you need to be able to tighten the skin.