That looked to be a crease in the tape that you laid down previously. And yes, that will most likely show, Only way to get rid of it is to cut the creases off and lay the other piece nice and flat with no air bubbles. As for the pen bodies, that works pretty well. Be sure to put a Popsicle stick on teh front and back of hte wing so that the rubber bands don't distort the wing as much.