The rattle and knocking sound seems to be a common trait. That is right near the torque spike region where the engine is producing maximum torque and the Centa unit is desperately trying to absorb it. I think if you kept at that range long enough the Centa unit would discombobulate or something. I remember writing of this years ago when I put out some general guidelines on running this beast. The manual says to avoid lugging the engine at or below 2700 rpm. That's straight out of the S&S engine manual written for bikes. I would say that the real lower limit would be about 3000 rpm due to the increased weight of the car. As for ty[ical running I've found that 3700 rpm through the mid 4000's is the real sweet spot for this car. Everything smoothes out.

I had to replace the original H-D compensator at around 22,000 miles. It died catastrophically as in: It did not go... My current Centa unit has over 30,000 miles and during the chassis rebuild the dealer pulled the Centa rubber cylinders out and they looked barely used. They were replaced with a new formulation since the unit was out but it was not necessary.

This car is a torque monster. Never forget

What's your mileage? Who cares. Is it practical? See #1. What happens when it rains? You get wet.