I'll second the KAB Speed Strobe. I use on on my Galibier and really like it. Remember, anytime you check the speed be sure to have the stylus tracking in as dynamic a passage of music you have.
As far as what you may be able to do if your table is a bit off, that's a bit tougher. You may be able to play with the belt tension, and maybe even material, to improve things if the speed is not off too much.