I hope you build a plane and come race as this racing is taking off here on the west coast. come join in the fun!

515 square inch for up to a 1.19 Cu four stroke. has to be wing area tail doesn't help. No minimum weight but most built up race planes are 6 pounds or more for the 1.15. I wouldnt worry about weight as a 8 pound plane can run the number with a YS 1.15 engine. No thickness rule either. just build a plane that is strong enough for 180 mph.

http://sacramento-rc-flyers.org/samwarbirdrules.html