I guess im wondering what you do differently? Do those belts have any danger of damaging the carpet? They will probably help a great deal, but if they slip they are going to really make a mess.
Your probably not the only team that can pull people around on tile. I bet my team's robot could do that, we just didn't try. Remember that friction = u * Fn so you either increase the coeficient of friction or the force normal. Traction is different, and it looks like traction is what you exel at.
heres a video:
www.startateam.com/639/movies/2002_build_1.mpg
Hope to see you guys do well.
Greg