Misfire at cruise, popping/afterfire at 3000RPM

Phreakish said

Not that anyone above is off the mark, but no amount of ignition fiddling will fix a mechanical problem, then again no amount of mechanical fiddling will fix an ignition problem either!

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Very true!
But wrong ignition can cause mechanical damage.

Righty Tighty said

I got 37 degrees at 2800 RPM, but the engine stumbled and stuttered at anything higher than that.

Took it on the road, and a light cruise revealed no misfires. Little heavier on the throttle, good to go. But again, anything over 3/4 throttle or say, 2800-3000 RPM, stumbles and falls on its face. No more afterfires, though.

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So we still have little idea what the timing looks like, but now know it was 41*BTDC at 2800 rpm.
Yes that could damage at full throttle.
Whether it did cause mechanical damage or not, definately want to avoid going close to full power with too much timing lead.