TC
You've brought the pedant out in me.
You wrote 'the a/c would pitch down automatically due to the impingeing air from below on the stabilisers. Most helo pilots end up having to contain the amount of nose down that occurs for this very reason.'
The nose down pitch of a helicopter in cruise flight as a secondary effect of lowering the collective (or the nose up pitch from raising the lever) is due to 'V squared' effects of advancing v retreating blade and subsequent phase lag acting 90 degrees later. It's got nothing to do with the upwash/downwash on the horizontal stab - have you seen the size of the R22 stab? This can be seen in flight as the pitch up/down is instantaneous, long before any RoD flow has had chance to develop.
Back to the topic..........
JJ