I made the same mistake the when I first got it too.  The next model down is smaller in width so not as much of a problem, but I liked the rubber mat and it was a bit more heavy duty.

I put some double sided tape on the underside of the mat so it never moves.  The only downside is that the rear wheels are fixed, so you cannot move it sideways but once you're use to it no dramas.  I also moved the silver handle as its not needed for pinball application.