Re: Dent in gas tank?
Might be a good idea to glue a disc or thick rubber to the foot of the clamp so that the sharp edges of the clamp don't make sharp crescent shaped impressions in the tank. or grind and file the foot to slightly concave shape with edges well rounded. Instead of squeesing the clamp, you may be able to "hammer the dent inside the tank with the clamp body or a welded up dolly.
Don't expect great results without using bondo though.