Hot tent stove jack opening

I would think that it will be difficult for the pipe not to touch and maybe the more air tight it is the better it would work.

Some have an expandable gasket like this :

but an x would be simpler to do .

It’s fine to have the pipe touching the jack fabric. In fact, that’s the only thing stabilizing the pipe. You can cut a spoke-shape (the multi-armed ‘X’ in the first pic) into the fabric with an oval outer radius so that the pipe rests against the folded base of the lobes when inserted. That’s more durable that cutting an oval completely out and having the pipe lean against a cut fabric edge. Start with the horizontal spokes 2.5” across (total: the pipe diameter) and the vertical about 3” to accommodate the slope of the shelter wall. 8 spokes total should do it (at noon, 1:30, 3:00, 4:30, 6:00, etc). Practice first on a scrap of fabric if you don’t want to commit immediately to the shape.