Yamato II was able to move, just not very fast...
The problem seems to be in the configuration of the propulsors. Yamato II used pod-like two units, each with six small MHD thruster pipes. This leads to a massive increase in skin friction and resistance, but was necessary to reduce the gap the M-field had to cover. You'd need somewhat more powerful magnets to be able to use wider tubes or the open "plate" used for tank-testing. The 6-tube arrangement had a nifty side effect - the field lines were constrained into a small cylinder of volume, and so it was safe for an individual fitted with a pacemaker to stand on the upperdeck over the propulsors.
RP1