Chris,
I used to be a member of the SCTA when I worked over there (SoCal), came home in 1996 and haven't sat on a trials bike since! Has anyone thought about going through the various clubs membership records say for the last 10 years and see how many ex members are no longer and hitting them up with a mailshot? There must also be a whole bunch of people in the area that used to ride way back when and have an old twin shock bike gathering dust in their garage/shed, how about a class aimed at them at ATA events? Say hello to Dwane Stone, Mark Oldar, John Thompson for me (Pete Thatcher) will you