Yesterday I noticed a 1ft in diameter bubble under the rubber in the roof by the rear ac unit. It is a 91 allegro bay. I see no tears or holes but obviously there is a leak somewhere. It has not leaked into the coach. I am assuming (which I should know better) that I will have to cut out a portion of the rubber, see if there is any damage to the underlayment which I believe to be wood. Then glue down a piece of rubber roofing. Any tips, tricks, advise would be helpful. Thanks in advance for all of your help. Also I am a tightwad and any advice on where I can get the products I need for the repair cheep would be greatly appreciated.