I would recommend you put it further from the corners for couple reasons. Maybe 9 or 12" instead. 6" is the minimum for the 1100c. You have a big hearth with plenty of wiggle room and bringing it away from the wall will bring the flue centerline deeper in the room which may be a better match for a larger stove if you upgrade. Ray, tiles should be set in latex modified thinset. If using large stone or brick, I think type S mortar is recommended.