Okay, just pulled a standard Shimano road derailleur off my Raleigh which is mated to Shimano 8 speed downtube shifters and a Shimano 8 speed cassette. I installed the New Success derailleur, set the stops and installed the cable.
It shifts perfectly, and when I measured the parallelogram pivot points and cable anchor location they are identical to Ultegra.
Dave, you tried to make a shifter that wants to make 5mm shifts work on a 4.8 spaced Shimano cassette. A lot of relatively active and sophisticated tinkerers demonstrate little awareness of the mechanical aspects of different shift systems. Cassette spacing matters.