The New Era one is universal. They fit the .21 - .32... The mounts are just like the ones i am having made. If you need a mount, i can sell you one (i have someone else waiting for one on here as well). Ask away... this is my specialty!
I'm going to stick to the normal .12. I have a V-Spec but all the mounts are for P/S engines. .21Rc10GT you should try out those 1/8th scale wheel adapter be NewEra, help get the power to the ground!