On a .12 engine It's advisable not going 0.10mm over or under 0.46mm, so that is 0.36mm or 0.56mm of total head clearance at sea level, with the lower number suitable for 16% nitro and the higher number for 30%.

Generally on a .12 engine 0.10mm will change the compression ratio about 3/4to 1 point..

One last comment. never assume that the head shim that is on the engine is the actual head clearance. In some cases you will find that the engine actually has 0.20mm to 0.15mm without any head shim. For example if an engine has a tolerance of 0.20mm without one, and the factory installs a 0.30mm shim, it gives the engine 0.50mm stock head clearance.
When in doubt measure the head button register and the piston to the top of the liner at top dead center and subtract, to determine proper shim. This is the only way to really know.

AFM