16" is considered optimal for velocity with most 22LR, accuracy may be another story, it really depends on alot more than the barrel, but i wouldn't go too short if you still want accuracy...
in theory the shorter the barrel, the more accurate it *should* be, on the premis that a shorter barrel is stiffer and by nature has less harmonics. that was the opinion expressed by tony kidd of kid innovative design.
that being said, i was gonna play around with a 12-14" kid .920 barrell, but they became very unavailable in canada. so i went a different direction.
if i could souce one for a decet price, i would still buy a barrel, and then buy another 10/22 to put it on to test the accuracy.