What is your concern pertaining to gluing a thermal pad to the floor?

Are you worried about moisture, or adhesion?

A sheet of polished stainless screwed to the bottom of the floor would certainly make a difference. Wrapping the mufflers will help significantly, but the wrap is delicate and will be hanging in tatters the first time you scrub. A heat shield with an air gap welded to the tops of the mufflers should also work well.