Pick A Linear Heavyweight Champ To Beat Jeffries Under That Era's Rule Set

Small middleweights still hit hard enough to slice a man up and hit the target more often with a smaller glove. Three lighter punches are as good as one heavy blow and those smaller guys certainly landed with that ratio on Jeffries.

As for Jeffries needing more power to knockout men closer to his own size well Look at all the guys Ali stopped without hitting hard?

Grinding resistance itself will drain any man.

The thread calls to consider this with the rules of the time. That means gloves that allow not just less protection but the ability to grip and clasp more in the clinch, the extra distance and barbaric officiating.