bc, Could one construct a form for use w/the leveling compound (as w/concrete) to level just the section under the tub? We are carpeting the rest of the area. This is a long rectangular bathroom (or will be anyway) 5.5' x 15' with the bathtub tucked in one end, so we are not too tight as nothing else in in there at the moment. Are you familiar with the maximum "degree of unlevelness" that the leveling compound should be used to correct? Thanks for your response(s)!