I think the only critical measurement for Hercs is functional reach. I seem to recall that a co-pilot with stumpy arms can't reach the No1 engine fire extinguisher handle when strapped in. But there wouldn't be any height restriction. I'm not sure what restrictions there might be on the rotary fleet, I would have thought functional reach would be the only stopper.
The problem is that all pilot candidates have to be fit for the FJ route (with very rare exceptions), so you have to be within the limiting measurements, which I think, as mentioned above are currently based on the Hawk.
The gist is that, if you are built to standard proportions, you should be OK up to the height 6'2"ish. But when you get taller than this, there is a good chance that your hip to thigh length could be an issue.