I had to fix a flatty on my 20" uni the other day and then before I put the wheel back on the frame I had a quick go at tryin to ride it as an ultimate wheel. I could do a jump mount and do 2 pedals but it was pretty hard.
Does anyone actually buy these things or do they just try and ride their unicycles without the frame attached?
Most people I know that own one have made it themselves. It is pretty cheap and easy. The Lower Q factor on a disk UW makes it a bit easier than a unicycle wheel.