Jim, I like the long rods and light pistons idea. However I suspect many guys do not get the most out of relatively unmodified engines I use methanol fuel, so it is easier to get jetting and ignition advance right. I would like aluminiun barrels, but the motor would probably run too cool. If you use petrol as fuel when racing with a standard motor, the heat build-up must become a problem as you approach the tuning optimum. Most guys probably do not get near that point.
In the 1950s in Australia, the guys used to run Manx Nortons on methanol, and became accustomed to high speeds. When they went to the UK, they found the Brits could get their Manx Nortons going just as fast using pool petrol. Manx Nortons do not have cast iron barrels. I remember Steve Oszko telling me he used to warm-up his Manx very carefully prior to racing - he always used methanol.
The Commando 850 motor is much better then I ever expected, even unmodified. Mine has had alomst nothing done to it, and it is still fast enough.
