@helispotter: I very much doubt, that a model helicopter would be appropriate for this kind of test. The problem does not lie in the mass and engine response, but in the dynamics of the main rotor. Building a scaled down model of the rotor with all the correct flexing and flapping isn't as easy as it sounds. The commercially available models lack a lot of components of a real rotor. No flapping- or lead/lag hinges for example. Not even virtual hinges in the blade root. Model helicopters do not need that. And then there is the Reynolds number.
But it has been done to visualise VRS in wind tunnels. But here they want to fly certain manoeuvres and that is difficult in a wind tunnel.
The budget isn't very high. I think for that money it is cheaper to use a real helicopter.