Interesting thread and I always enjoy your posts 'Downunder'. I even reckon the emu looks like a friend of mine.

Not sure I completely agree that you cant do much about compression.

In the early 90's pattern scene, we used the Hanno engine. The greater the nitro content the less compression we ran. OS even provided a different assortment of rings to place between the head and liner. This allowed the pipe to be less critical, but still gain the benefits of the supposed more calorific value of the nitro.

Many a pattern flyer was running up to 35% nitro using two rings.

I'll be interested to read your thoughts.

Cheers

Phil