It's been discussed previous. Gov-lock as designed is about as good as it's going to get for an automatic locker with no external controls. (of whats now available...if they could beef the mechanism/carrier it would be better) Increase sensitivity, you would likely start having problems when turning and what not.
For a vehicle you are easy on, the gov-lock is about the best of all worlds. When you start beating them with larger tires, wheelspin, and/or lots of throttle, they show their weakness.
Spectacular failures happen with any of the carriers apparently, but it's most common for the small diff's to break the carrier in half, while the larger ones just break the weakest link, the gears.