I have completed fabricating and installing the Lift Reserve Indicator (LRI). I don't remember where I got the write-up, but if you're interested you can Google it up.
Basically it consists of a probe that you must fabricate, which consists mainly drilling a few holes reasonably accurate, and purchasing a differential pressure gauge with a range of 0 to 2 inches of water.
I've just completed calibrating the probe angle relative to the bottom surface of the wing and test flying. At the moment, the airspeed indicator is toast so I haven't had the opportunity to really get serious evaluating the setup. I'll write more as I become smarter.