McNeil, I also made that V on the base heh. Simple solution after my stupid prototype. However instad of buttons I use hotwheels. There're many to choose from, be patient and go thru their whole stock. I found some really nice thick and big wheels yet light, out of their 1930's (dick tracy style) collections.

Other nice wheels to use are the cheap china bus and taxi ones. These come with rubber wheels for good traction.