I'm another one that started with 19:47, then switched to 21:47 (now on 19:42 we'll close)
21:47 is the most you want to run on a stock bike. I used to run a thunderbolt that had 22:47, it would go some too but there was a lot of clutch slip setting off, which resulted In a lot Of clutch issues. When I attended the Danish Rally i was running 20:42 which is a tad taller still with a close ratio box. My bike was setup to give a lot of torque at lower revs so it worked ok, it would cruise at 75 all day long but on the ride outs where the runs are slower it wasn't much fun. So I dropped to 19:42 and returned to the standard gearbox. Still running a small port head... and that makes a big difference in tractability.