Hi Robin,
You can use 33% in your Alpha, just use the extra 0.1 headshim that came with the engine.
I tested a Alpha 850 for Jaap Dienaar and used also 33% nitro on that engine, works fine.
The engine reacted a little more crisp on the bottem end and tuned very easy.
I youst the OS P4 glowplug wen testing that engine, worked perfect.