It depends on the CH advance. If it has none, then start at 20 degrees before TDC. You will probably end up running full bore at about 25 - 28 degrees.
If you use the piston position method, start with 0.8mm BTDC.
Do not advance ignition timing beyond the point of best power. It will make for a mean engine if you do. Better back off very slightly. This allows for higher rpm as the prop unwinds.