Rotor first, plank later.
There are apparently some issues with high time plank riders, when they hear the horn go off, they lower the nose, which is the wrong thing to do in a helicopter when the RPM low horn goes off.
During my plank check ride the examiner pulled the throttle on me and I descended in an helicopter autorotation stile glide slope to a bush runway on my left side (helicopter pilot heaven if you want). Side slip and everything one can think of to have steep glide angle and not too much speed. I would have made it ... to the other end of the runway probably, but we climbed away and he showed me again the point where he pulled the throttle. There it was, a nice long concrete runway right in front of me (behind the spinner I would say), way beyond the glide path of the helicopter, but well within the reach of a plank. Thankfully the examiner was dual rated and I think he knew exactly what was coming. I think it can be difficult to shake off all the habits one have but it works for many experienced guys out there who are dual rated. Would not worry too much, but be aware of it.