No disrespect in turn to you RPM but it's the first I've heard about Negative G/Mast bumping in this case. And the source of this is as close as you will get to an official Torrance factory statement.
I'd be willing to bet that there was a massive, collective sigh of relief emanating in California when they found that out. I'm sure this forum will be a livelier place for the next few days (R66, mast bumping, same old Robinson problems etc).