I doubt the tolerance, don't think its possible. I use the concentrate pad under the Ceramic filter and Like swimer, I point the torch at the filter, NOT the glass, the only difference I suppose would be that only the center of my ceramic filter get red and only slightly, I move the torch to ensure it.
Single pull, if you are not completing you are doing something wrong possibly including small lung capacity.
I do not pre-melt or pre-heat.
Two ceramic filters???? Also GVG sells a concentrate pad not a liquid pad, volcano sells a liquid pad
I realize that no one book, one person, or even one ideology will have all the answers. I believe my job is to remain open yet discriminating. My intuition helps me discern truth, and wisdom helps me identify malicious intentions.