I am installing a napoleon 1100c stove my question is: shouldnt the adapter (simpson# 8679) fit over the flange on the stove? It fits inside of the flange. it also has 3 holes in the stove flange, which I assume are for fastening the adapter to the stove but the outer wall of the adapter make it impossible to do this once installed. does anyone know the proper way to do this? Thank you very much!!