1213 used this:
Each was a bit over built at 7-1/4 lbs. Should be able to take 1/2 lb. or so off.
Speed was 7-1/2 FPS with 4" wheels - that's with the Chippy driving the pins on the first stage of the DeWalt - I.E. planet gears replaced with adaptor keyed to the Chippy output shaft.
Mobility was outstanding with 95A durometer urethane wheels. Pushing was not much of an issue last year, but we managed to push when we needed to.
A chain added to connect front to back wheels would transfer power in case one end got lifted - but, I'd rather stay low a use a ramp than bother with chains.