i know people said 20/49 gearing instead of 21/49 gearing helps tons with heat which seems weird since its only 4 mph slower. not really much of a gear change.
i think the clutch sheeves and belt feel the difference. I went to a 20 tooth and 7 tooth drivers this year compared to last (which is a 12-13% drop in gearing) and honestly it wasn't a night and day difference.