ACtually Schedule I of the CAMS manual (http://www.camsmanual.com.au/pdf/10_gen_req/GQ10_Schedule_I_Q411.pdf) covers off their requirements (and recommendations), but fundamentally the shoulder straps should be horizontal to the shoulders, and as short as possible
The standard seat belt mounts are not OK according to CAMS because it is more than 40o downwards from the shoulders.
Zeb, this is the 5th car we've built over 10 years, and the biggest thing I've learned is racing is incredibly hard on cars. Anything that is not 100% OK will catch you out sooner or later - so do it right the first time. Neat is OK, but it more important to be simple and quality/reliable.