I built a "temporary" crosscut sled for stock that can't be cut safely using the miter gauge (small parts). It uses only one of the saw's miter slots rather than both of them or the edge of the saw table.
A test cut results in an error of about 1/32 inch over the 7 inch metal leg of a try square which works out to about 1/4 degree. Not good enough for cutting miters but I'm wondering how well others have done getting their sleds dead on and whether you consider 1/4 degree good enough for most woodworking. Is it unrealistic to expect dead-on accuracy using a single slot?
Note. I've checked my measuring tools independently and against one another. They seem to be fine, though I'll check again in the light of day.
I'm eventually going to build a panel cutting sled that uses two guideways (both miter slots or a miter slot and the edge of the saw table) in order to avoid this problem.