Our rules are no moving parts so the weight has to be solidly mounted. Thats also why I didn't make the boom operational!! Also we can polish wheels but can't remove material from them except on the hubs. There you can remove some so there is not as much friction rubbing against the car. Keys are polishing the axles (get rid of the burr on the nail head), put all the weight at the rear so it pushes for a split second longer, move the axles as close to the front and rear of the car as allowed to increase the wheel base (when doing so also look if you can mount one front wheel slightly high so it actually doesn't contact ground to reduce rolling resistance) and be sure wheels/axles are as true as possible. I didn't spend as much time on trueing up wheels as I should have this year. Last years car would've kicked butt but my wife had the wrong date on the calendar so I was still painting the car after the race had already been held!