[joek]

buy them individually.

we had no problems with mechanum in 2010, just with everything else falling apart... the bumps were hard on it. depending on your strategy, there may be no need to cross the bump. however, the bridges will be fairly slippery.

i've been toying with the idea of having a pair of powered kop wheels that could be pushed down when needed, and lifted off the ground when not. I figure that they would overcome the mechanum's lack of traction, while still allowing strafing when not in use.