Gliders use ballast to increase theire weight in order to glide faster.  Gliders, like any other airplane, glide the farthest when flying at the angle of attack for best L/D.  If you want to win a glider race, you want the speed for best L/D to be as fast as possible.  You do this by making the airplane as heavy as possible.  The glide angle is unaffected (to first order) but you travel down that slope at a higher speed.  Note that the sink rate increases dramatically, and glider pilots just trying to stay aloft want to minimize the sink rate, so they don't use ballast.

Your suspicion is correct -- the next time there's a Lancair GLIDING race, he with the heaviest airplane will win.  (Hey, there's an idea!)

- Rob Wolf