Last year we purchased the specified casters and some "cheaper" ones. The goals made with the cheaper ones were CONSIDERABLY HARDER TO MOVE. In fact, after forgetting about the mixed casters, we decided that there would be lots of variation in goal resistance and decided to not try to drag goals around. Oops. In fact with the casters specified the goals are pretty easy to move around.
Well, let me qualify that: we used the "good" casters from last year. Perhaps this year FIRST spec'd the cheaper ones that Home Depot sells. I better check that out before we repeat last years mistake.
We too, use the Bosch in low gear with a final drive of 3:1. Plenty of power to slip wheels on the carpet. With gear switching, top speed is a respectable 10fps as well. (6" wheels turned down to 5.75" - flat)
Cheers!
Team #492