jtatarin: inverted hover will use another of the buttons on your radio, (Idle Up), and some mixing called "Pitch Curve".

Basically:

The idle up button allows you to set a constant rpm, regardless of the position of the left stick.

The pitch curve allows you to set sufficient positive and negative collective pitch, (you'll usually see a range of -10 to +10), based on the position of the left stick.

For an inverted hover: engage the idle up, (so the rpm won't be affected by the left stick), flip your bird over and pull back on the left stick 'til you get about 6 degrees of "negative" pitch.

Although you pulled the stick to a "negative" position, the bird's upside down so it actually has positive pitch - and about 6 degrees should let you hover.

If only it was as simple as it sounds!

So far I've only tried it on a sim: I can keep it inverted and off the ground, but I haven't been able to even approximate a hover that way yet!!