Swapped the spark plug, tried again. Ended up dropping down from 80 main jet to a 75 (supposedly, it's from the clone carb so who knows).
Crunching the numbers shows close to 6hp now vs 5hp, and a solid improvement in average torque during the acceleration phase, from about 2.2ft-lb to 2.9.
Still doesn't seem to want to rev out as much as expected.