Re: Harsh Smoke
One 40mm should be fine. Try packing the tobacco just under the brim (if you look to the bowl from the side) and make sure the foil is really tight. Not \____/ but -------- (if you know what I mean). Sometimes when the foil is not tight it will go down in the middle, so it can touch the tobacco, even if you pack it under the brim.
You can also try to cut 1 40mm in half, heat the 2 pieces and put them both on the edge of the bowl. Good luck!