Thanks. Answered not only my main question, but also explains the reason for tail rotors not being driven via the head. Especially on a really small heli it would definately be bad to bleed the energy to the tail which is useless for an emergency autorotation.

I was worried that certain 30 size heli's might be permanently engineered to be not-head-driven on the tail. But you say that you can change that in the mechanics? That's what I was hoping to here. I'm thinking of getting the Raptor 30 v2. Is a 30 size not sort of on the borderline in this regard? In other words that the tail could be head driven while still being able to autorotate reasonably well?

But it's also a good option to adjust the low end engine rpm.

Thanks