Kewl! For tougher hard plastic, I use hot-water moldable plastic beads like the ones at
http://www.micsaund.com/2006/03/13/plastic-you-can-mold-in-your-home-for-diy-projects/ . I've found them pretty cheap in clear plastic clamshells or bags in various "junk" shops, and they work great.
I'm planning to use it to mold a dihedral nose piece for a glider-kite (any day now!), and I've already used it to make a few finger-joint splints that I liked way better than the ones from the Sports Medicine clinic.
It's pretty tough stuff, and you can roll it into sheets or balls or whatever.
The finished product is a bit tougher and a tad more flexible than what you'd get from those co-axial epoxy-putty sticks (like Ding Stick, etc.). Maybe a tad heavier, too, but you wouldn't need as much. And it's ready to go as soon as it cools to room temperature.
Really no disadvantages at all, as long as (a) you don't burn your fingers when you first take it out of the hot water and (b) you don't use it to make a part that has to stand up to heat.
