Self-professed Prieure de Sion expert, Paul Smith has recently written an article of his findings that the POS was a hoax. His research over the years has been quite convincing.
I must admit to having an addictive fascination for the whole saga since reading Holy Blood, Holy Grail many years ago. The *sacred geometry* leaves me amazed as well.
For anyone who may be interested, you can read Paul's article here:
http://mailbox.univie.ac.at/~muehleb9/renneslechateau.html
Thanks for the reference. The whole topic is indeed a fascinating mix of history, religion and folklore.