Thanks Pete, I might try that. That would probably insulate better than the pine bark mulch I was considering using. I'd like to reuse whatever I insulate with, shavings can go on the blueberries come spring.
Pino, from what I've read it takes a looooooong time for something like that to drop soil pH appreciably (that goes for needles, pine bark, etc). I doubt it would be enough to effect figs, but one could just toss on some lime to be safe. That doesn't mean I don't use pine products on my blueberries and other acid lovers, but I don't expect them drop the pH alone.