Thanks for the clarification on that. I've used it on reinforced EVA foam without problems but not styrofoam. I'd hate to lead someone wrong! My only dissent would be the bit about application. If you're patient when applying bondo, doing small areas at a time, and take the time beforehand to trim protrusions off while it's curing, you can save yourself an incredible amount of sanding. The biggest mistake I made when I started with bondo was over-application. It's definitely sanding intensive either way, I won't lie, but it's the difference between it being an insufferable amount of sanding and a reasonable amount.
"The important thing is no one was hurt... No one who counts."