You know what, guys, I dare you to do an experiment on this.
Get one of your old robot, or a cart with something heavy on it, and put on some rover wheels you are supposed to use this year. Lock the wheels, and pull the robot or the cart with a hook scale. Figure out the maximum amount of force before slipping, and the amount of force you need to keep it slipping.
Then keep everything the same, except putting more rover wheels on, and try again. I dare you to report your finding from this experiment
. I dare you to let the FIRST community knows how exactly these wheels are going to work on the crater surface.
Nothing beats a quick and dirty experiment you can rig up in 30 mins.