Dale, the difference between your carb jetting and Roy's might be in the exhaust system. If his is freer flowing (read: louder! <chuckle>) that certainly could make the diff.
Density altitude could be another factor. If Roy's bike is "seeing" lower numbers than your bike, it would need to be at least a bit richer.
Yet another consideration is ignition. If Roy has Nology coils and wires, this would let him run slightly richer, too.
One more idea: bigger cams reduce signal to the carbs, so you usually need to rejet richer on just that basis.
It all adds up in the end.
