Hi. I am planning to install a QuadraFire gas insert into a masonry fireplace with a stone veneer wall. The stones are quite thick and uneven. Does the surround panel have to fit completely flush against the wall? The manufacturer claims that there are pieces of insulation that will fill in the gaps between the surround and the stone wall. The technician who cleaned my chimney said that I have to put mortar or Wonderboard over the stone to create a flat surface before installing the insert. I'm not sure who to believe at this point.

Thanks,

Bob