According to FAQ #3 on this page
of this site, the two-person sparring set was created by a student of Yang Chengfu named Chen Yanling. On the east coast of the U.S., Jay Dunbar & Kathleen Cusick are known for running a seminar on this set, and you can find more information about it here
There is also a description and analysis of one version of the set in Advanced Yang Style Tai Chi Chuan, Volume Two: Martial Applications
by Dr. Yang Jwing-Ming, pp 160-215. A more recent book, Tai Chi Chuan Martial Applications
seems to have the same information listed in its Table of Contents, but I have only examined it on the amazon.com site (click on Search inside this book
) and cannot confirm that it is the same information.
I have seen a little of this set in person, since one of my former teachers knew one side of it. It looked quite interesting and contained some applications I had not seen before. I believe it can be done with constant contact or with at least some disconnection. Others may have better information. I was quite keen to learn the set at one point, but now have learned enough traditional applications and moving step patterns that I am not looking for more forms to learn.
I hope this helps.