I have bought a solid marble tub, and am running into issues getting it installed. The assembly that came with it (bought from an importer guy, supposedly, and had a drain with it. problem is that set the pop up won't reach the tub to seal. bought a piece from kohler, but it is 1 1/2 inches long, and the tub is really thick so it isn't long enough to get snugged in right. Plumber says I need a 2" pipe, about, but it doesn't seem they make one. Any suggestions?