We've been looking at engineered wood floors (concrete slab installation) for a while and haven't seen anything more than 7 ply, all 3/8" or 1/2" thickness) in engineered flooring until yesterday. I've also read info on engineered wood that says up to 7 plies -- 7 being the best. Yesterday, I brought home a 9 ply, 3/4" sample. It seems really solid, is one of our 2 or 3 favorites, but I'm not finding much on it in researching it. One of my questions is whether the 9-ply, 9 coats of finish and thicker construction necessarily means anything about the product, good or bad?