FWIW, based on what I've read it seems that advanced timing is only needed if the ratio of gearing/displacement given some power output isn't optimal. The lower the air&fuel to cylinder volume ratio, which corresponds to lower torque, the farther apart in the cylinder pockets of air/fuel can be, and the sooner ignition needs to start to get all the air/fuel burning up around TDC. W/ pockets that may be farther away, retarded ignition may not result in everything igniting until after TDC. W/ proper gearing and greater torque, the mixture is more or less homogeneous, and in this case even/consistent ignition of the whole mass in the cylinder is much more likely.
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