My method was:

Short twisty circuit with no long straights = tight piston/bore, advanced timing, high comp.

Long fast circuit, flat out forever = loose piston/bore, retarded timing, low comp.

Reasoning:

On a short circuit with only short bursts of acceleration there's little chance of excessive heat build up/piston growth, so you can run a tighter clearance. The high comp and advanced timing is relative of course, but this gives good punch out of corners, but little over rev.

On a fast flat out forever track the opposite of above is true.


As for ring end gap, affecting the power. I'd say not a lot, if you're talking the difference between 0.24mm and 0.35mm on a new ring. The power loss comes from the loss of pressure of the ring against the bore when the ring is worn. A keystone ring does help here of course, as it is mechanically forced against the bore wall by design.