C-
Don't ground them down. Sand the bottoms with a 600 grit wet or dry paper,
then follow up with successively finer steel wool application, always moving
with front to back motion. Follow up each sled use by drying off the runners,
and before using the sled each time, do the steel wool thing again. I've also
buffed the suckers with rouge on a buffing wheel but this is a bit much to
expect from a New Yorker. The closer you can get to a polished surface the
faster your Flyer will go.
Don laNiege