Hi all. I'm getting ready to install a Napoleon 1402 and full liner. My hearth is flush with the floor level and shy of the 16" front clearance and I plan on using black stoveboard in front during the burning season and removing it in the off season. I understand it's 5/8" thick so am wondering if there is any harm in raising the insert up off the hearth 3/4 to 1" for clearance for the air control. Seems that some firebrick (if it's available in the right thickness) or even steel would be OK. Would any of this affect the air flow with more space under the insert?