He can still use that backing, and either way, with the wall back there, it is a challenge. if you use the backer, rub a very thin coating of vaseline over the either back of the tank. then take a credit card and smooth it out and you will have a bubbless backing that will last for years. that is what I had on my old 75 and it looked painted. works great and will definately last and is 100% reversible. Painting it would work as well. just roll it on with a roller. Not sure how much room you have behind the tank, but either way you will have fun when you get to the center of a 6' tank!