I'd suggest calling the track and seeing how turnout is for the classes that interest you.

Out here the 4wd class at 2 of the closer tracks is technically open, with one of them being small enough (the track) that it really ccomes down to driver, fastest guys are running 13.5 . The new track here I run 13.5 in open and I love the power delivery. I would say if the club spec interests you, give it a try.

Other tracks in the region have gone to spec 13.5 for 4wd. Its definitely growing.