I got a styrofoam knife at Joanne fabrics. I guess that's a different breed of cat than I needed. It had a 5" 'blade' made of some kind of very light metal. While I was trying to cut the foam, it ended up bending, so that didn't work out at all.
Folding them in half and rolling sounds really good and is probably what I am going to do. Will it leave a permanent crease? Probably look like carrying a beer keg, but better that than a bongo drum.
I'll have to think a little more about Brandon's idea. If I was going to go that way, I think I'd probably try the Sgt Rock method (a wider piece of pad at the shoulders), but I'm still inclined towards the SPE idea.
I can't wait for the time I can use the 1/4" pad! It's only 8 oz! yay!