We went with cantilevered mecanum wheels with hex bores. We did this for ease of maintenance on the wheels, so we could easily take them off. We had bumpers (that had abs blocks that slid into the chassis aluminum tubing) around its perimeter to protect the wheels.
We had addition reduction with another gearbox on the output of the banebots planetary. Disassembling this drive to check for maintenance was no problem because everything just slid apart after we loosened some nuts and bolts.
Our team had been sort of scared of cantilevered wheels and the effects it would have on the shaft, chassis, bearings, and such. It turned out working really well.
Below is a render of the drive.
