The Dominion helicopters use a governor. The Dominion 3D 90 uses 1750 for ID1 and 1800 for ID2. The Dominion 3D (60 size) uses 1800 for both ID1 and ID2. Either way, the ID1 settings provide plenty of rotor speed for aerobatics.
The problem is often that the throttle trim is not centered. The reason that this is a problem is that the Interlink controller doesn't actually generate a channel 6 for pitch that is seperate from the throttle like a real radio does. When you move the throttle trim up, it moves the bottom of the collective pitch curve up. You can verify this pretty easily...
- click Aircraft | Edit Aircraft.
- Browse to Airframe | Fuselage | Main Rotor.
- Scroll down so you can see the Collective Pitch entry.
- Center the throttle trim.
- Move the collective stick up/down and look at the values. They should be very close to +/- 10.
- Move the trimmer to full low.
- Move the collective stick up/down and look at the values. They will be -10 to 6.9.
- Move the trimmer to full high.
- Move the collective stick up/down and look at the values. The will be -6.9 to 10.
I had no problem flying inverted with the trimmer in either direction. Even with -7 degrees the dominion flies inverted just fine. Are you using an edited version of the Dominion?