Has anyone ever................

If this is really keeping you up at night, the solution is simple. Bolt the appropriate cranks into the appropriate blocks, bolt a belt adapter to the crank flanges and an encoder wheel to the crank snout, and power the cranks with a supply of lube by an electric motor; no rods, no pistons, no cam drive.

Pick an RPM to run them at and see how much current it takes to spin each at the given RPM. The difference in current can then be easily converted to the hp gain/loss for a given crank.

As I said, too many variables to measure in an applied example, but the difference in drag: quite simple.

If you have these kinds of questions, get a Shigley's and start going to college. You'll do well in life.