In the 30's, 40'2 and 50's they used to race the rigid framed big twins off road. Harley's XR750 dominated flat track racing in the US for years. Because of the uneven way the motors fire is seems to make it perfect for sliding in the dirt. Having ridden Harleys for 30 years I can attest to how good they slide in the dirt. The rigid frames are the best, but even the new ones go pretty good sideways on the dirt. Fatboy and Heritage would be the pick if you wanted to hit the footy oval on a dewy morning.
Next time you pass a Harley dealership drop in and ask for a test slide.. err..I mean ride.