advance it until it wont rev anymore, then back it off a touch. thats where mine makes the most and widest power. i marked the degrees along my stator and do it that way. much easier.
On my bike, running lots of timing made it ping a bit in the midrange. better fuel solves that. or you can decrease the advance until that goes away.
i have had mine as high as 26 degrees. after making the squish band more like a squish band i'm down around 18-20.
dont get hung up on being bang on to some measurement. try it in a bunch of different spots and see what you like.