Drop-center drivetrains: Why?

[EricH]

It's simpler, unless the game requires pointing in one direction for any length of time (like 2 seconds to unload a game object). The defensive robots love 6WD robots that have omnis on the corners, something about they're easier to knock out of position rotationally.

A pneumatic center wheel on a drop-center is actually a pretty good idea: you can fine-tune the drop a little bit to get exactly the characteristics you want, even between matches.