Make sure you clean area well with acetone, alcohol, or Monokote trim solvent. I prefer the trim solvent--it really cleans well and the new covering sticks forever. Large areas such as between ribs, cut the entire bay out so the new covering can be sealed on the rib capstrips. It is difficult to get good results if you are trying to cover over unsupported areas. Also, a rounded edge does not come up as easily. For small holes, just cut little round circles of covering and iron 'em on. Simple.