If the heavy helo has to displace more air (same size disc) quicker to balance the mass (in the hover) then the speed of the downwash must be higher.
So you are saying that the lighter helo wouldŽnt have a downwash speed as high as the heavy helo?
(You can refer this question right to the which helo decelerates faster question)
We are up to the point, explaining why there are so raw windtunnel tests.
Greetings,