Thanks for your patience. I think this one should put me over the edge to be able to post more.
In case anyone looks at this, the 6-inch Festool foam cutting jigsaw blade does a decent job at cutting a roll of fiberglass. Still gets some threads, but if you are trimming your laps anyways it does not really matter. Slices through the pvc core like butter as well.
Nice! Good to know. Heard about guys using a metal blade on a bandsaw with the tape trick, guess I was thinking there was less to get snagged with the foam blades.
Thought I might have a case of chainsaw chaps on my hands if things went south.