Hi Dave,
What little I know about autos and synchromesh helos was relayed to me by a K-Max pilot who stopped at KTIX while ferrying a ship south-to-north. When he landed, I noticed that he didn't set the ship down like a feather, in fact he pretty much "plunked" it down.
I asked about autorotations, and indeed you are right, when the collective is below a certain setting, the mechanical mixing of the pedals reverses. I asked the same question about the transition point, and basically the pedals' "effect" goes to neutral as you go from full down throught the transition and into the "power" range of collective travel. Since in autorotation you pass through this "null zone" pretty quickly (both on entry and while cushioning), it's not an issue.
However, when setting down a lightly loaded K-Max, you start to lose some pedal touch just as you touch down, so the tendancy is to lower collective briskly on a normal touchdown.
(Or so he said - he could have easily been pulling my chain about this last part and just made a cheesy set-down, but since he was a factory pilot, I'll take his word for it!)