One thing that hasn't come up yet is the loading on the axles. Cantilevered axles have a much higher load bending loads on on them than axless that are supported on both sides. We opted to go with cantilevered shafts for the wider base and ease of maintenance (which proved to to be the right choice for us.) But we looked at the math and planned accordingly when picking shafts - 5/8" Igus shafting.
Despite some of the other problems we had relating to keyways and such, we never bent a shaft.
This spreadsheet should help clarify the math...