I've been running 35F / 37R racing temp (checked and reset between runs) on my Bridgestone Potenza S-04 Pole Position 205/255 setup (plan on changing to 225/255 at next tire change). Just make sure you chalk your tires so you can see how much rollover you're getting and you can dial in the pressure during the day.
Also just so you know 2015 SCCA rules has 97 - 08 Boxster in B street not C street
http://cdn.growassets.net/user_files/scca/downloads/000/003/742/2015-5-19_SCCA_Solo_Rules_book_online_reduced.pdf?1432652 746