Here's an interesting little book by Wang Xiang Zhai's student Kenichi Sawai:
http://www.scribd.com/doc/136940983/...-Kenichi-Sawai
It contains a lot of interesting information, including info on the history of xingyiquan.
I know master Sawai isn't great compared to modern fighters - but his insight and wisdom seem to me to be firmly based on true principles. Enjoy!
