Well, for the most part, it’s a 4/3 60deg. ship. The problem is not just a function of G loading, but dropping 2K lbs on the bottom side of a fully articulated main rotor system hub with no airspeed while falling over on its back. With the cyclic held back, no load, no collective, and inverted, that’s asking for a possible unsolicited roll-out that the flex beam head may not want to hold together for with a ton on it‘s bottom side. One thing we didn’t see in the videos was the ship doing a tight Cuban-8 or an Immelman. It has to do with the roll-out from inverted while still pulling the rotor disk back. From held inverted flight (Which the 530 can not do. The BO can, for a short time.) you can roll it out. But, not while passing/pulling through inverted. Keep in mind, that what you are telling the rotor system to do, and what the laws of physics can make it do, are often two different things. And note: When you push it around - Physics wins, every time.
Like the retreating blade stall we discussed in the other thread. The ship doesn’t begin to roll until it’s bleed off much of it’s speed from quickly (and unsolicited) pitching the nose up. Remember HS physics ? That gyroscopic phenomena called precession where what you asked for came out 90deg. down the rotation of the gyro? Same thing lives in every helicopters rotor system/disk. Because the rotor disk is a large, rotating mass, it will behave somewhat like a gyroscope. The effect of this is that a control input will usually be realized on the attached body at a position 90 degrees behind the control input. Now - Regardless of the control inputs. Let's take that disk and start pushing it around with momentum and gravity. Too much, and things like rotor heads start going on strike.

Just curious - I know you're into it. What do you fly?

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1980 300D - Veggie Burner !