when you are about to take off in a 47 with a throttle, (cam, correlator), box a small amount of positive pressure should be maintained on the throttle and a little bit more once the machine settles in the hover.
if you advance the throttle too much and back it of to maintain rpm prior to take of the rpm will always decay. try it.
this is because of the multiple connections between the throttle itself and the carbie, two uni joints, a slider, various rod ends and the cam box. lots of moving parts.
you can see the slack when the engine is running by rolling the throttle back and forth a little and seeing little to no change in the manifold pressure.
the best setup is on the early machines and the tom cat models that had a cable set up. you can raise and lower the collective as much as you like and you will maintain rpm. why they changed to the cam box has got me stuffed.
anyway the bottom line is that they are all different and you just have to get used to it.