I'm doing a couple bathrooms with 12x12 rectified porcelain so I picked up some of the tile levelers by QEP - the ones with the yellow wedges. Anybody familiar with this brand? They were inexpensive, but I noticed the "rocker" (curve) of the bottom seems kind of deep to me (like 3/16", maybe?). I could splurge on a Rubi kit at one of my tile suppliers if I have to, but wondering about these less expensive ones. Thanks.