I want to add a bluestone hearth slab to my existing fireplace. I have a Heat & Glow FB Grand LP Insert in an all-brick fireplace. The problem is that a 1-inch or 1.5 inch slab will prevent me from opening the access door at the bottom of the insert. Can I safely raise the entire firebox insert to clear the new slab? If so, what kind of material would I use? (I have room above the insert). PS - I didn't install the unit, but I just replaced the thermocouple in this insert, so I am pretty familiar with the "insides". My assumption is that there is enough "play" in the gas line and electrical connection (blower) to move "up" 1 inch.