Hi Motorman

If shiming theory applies for all .12 engines can you shed me some light on the following???
S12 Sirio Evo 2 head shiming: I measured cylinder recess with piston at top and got 2.45mm, measured head recess and got 2.00mm, so we have a difference of .45mm.
To use the engine with 20 - 25% nitro, what is the ideal total chamber one should have? I've read that it should be around .55mm, is this correct?. The engine comes stock with two copper shims, one is .10mm and the other is .15mm, so i could just use the .10mm, am i right?
Glow plugs: What is the equivalent of O'Donnells 77 and 99 on Novarossi??, because that is the only plug available down here.
AFM