Pinging again. I have been reading more about the piperjet single in
www.Avbuyer.com magazine. The April issue has a look at the aircraft, plus an interview with Jim Bass, big guy at Piper. They're going with the Williams engine, and expect to do 360 kts at altitude, competing with twins. Single engine, single pilot certification.
Oh, still hoping someone is working on one. If anyone knows, please let me know.