I'm working on the hearth pad for our new keystone, and have a question. We've got the 2" clearance around the chimney and it's firestopped with 26 gauge sheet metal. We built the plywood base away 2" plus a little and filled in that gap over the firestop with another piece of durock. We want to tile right up to the chimney so we ran the top of the hearth pad right to it. Seems like this should be fine, but wanted to consult he experts befor we payed the tile