' I've also had a stock steel Norton rod break in a short stroke 750, primarily due to the extra acid dip lightening that the factory mistakenly tried for weight saving.'
Are you saying the failure was due to hydrogen embrittlement ?
I use aluminium rods in my 850 motor, however the piston weight worries me. With the rebalanced crank and the way the motor is set up using methanol, it spins up extremely quickly as it comes up through the gears, even when the overall gearing is high. I always try to keep the revs below 7000 RPM, however it is not easy. Piston weight and those aluminium rods were the main reason I was always reluctant to race the bike. I simply did not believe in it. In fact the only reason I raced my 500cc short stroke Triumph for all those years was that it was almost indestructible.