I recently aquired a large acrylic tank that has 2 crack in the back of the overflow box due to the former owner resting a heater against it. I have purchased a sheet of acrylic and cut a patch to fit over the damages area, but I have a few questions prior to starting. First off, im going to use an adhesive call Surehold Plastic Surgery. I have heard a lot about Wel-don, but have not been able to find any locally. Plastic surgery has good reviews, and Im curious if anyone has had any experience with it. Secondly, surface prep - should i be lightly sanding to improve adhesion, or just leave as is, and clean thouroghly? Any help would be greatly appreciated.