Steve,
Traditionally SoCal has been using the best 12 out of 16 races in previous years and that was the number I got from Tim this year. The number of races for season points would have to be worked out with both the regional series director and regional NASA director (Ryan Flaherty) in your case.
The best 12 out of 16 races is a reasonable format which means you can drop two weekends because the NASA CCR 22.2.1 default is 10% or 1.6 races.
NorCal has a 8 weekend (16 races) season also. I worked out a special best of 10 races with/for my guys because of the economy.
We might be forced back to a best of 12 races next year because Jerry K. feels that is too many drops.