Try using vegetable oil between the black plastic film and the tank. It makes it stick and you can squeegee out the bubbles. They sell the aquarium stuff, but it's the fortune and also an oil. My black plastic background has a few wet spots, butmits a corner tank and I can easily get behind their to paint with a small foam roller. Next on the todo list. Once I saw the difference between black and blue, ill never change from black, especially in a reef tank. It pops big time.
Good luck