A better idea that I came up with last Spring was car tire tubes, cut the width of the belt from the outside/middle of the circumference for an endless loop belt - no splices.
Stretched to fit - no adjustable slides to mess with either.
All the tire tubes I found in the junk pile at the tire repair shop in town (freebies
), all tubes had mold lines on them that I followed, cutting the rubber with scissors with great accuracy in width.
A few conveyers is on my 'to-do list' too this winter.