Two things I've learned:
1) In fabrics, IFR is always better, and the extra expense, if any, is easily offset by the labor&materials cost to DIY.
2) I was always told that the pesticides used to treat
erosion cloth, (you know the jute/hemp product woven into about 1" holes, probably replaced by a plastic product these days), made it flame retardant. Totally untrue, as I discovered in the worst way possible when a flashpot caught the witch's well on fire during
Hansel & Gretel, before a live audience full of kids, in a 200-seat
black box theatre. Mind you, this was 26 years ago and I'm much wiser now, to the extent I won't go near pyro without a licensed pyrotechnician present.
3) Okay, three. The Dept. Chair of my college theatre used to sneak up behind every new
Stage Manager backstage during a quiet part of the show and say "Don't move, don't turn around. Tell me exactly where every fire extinguisher within 50' is, and what type it is." Those who failed got a long lecture after the show. Even today, when I take someone new up to our catwalks, I point out the alternate exits and fire extinguishers.