I've got an STS .28 and a hyper 7 - but I'd never put that beast in my buggy. I had to replace the entire drivetrain in my savage to be able to run the STS for more than a tank at a time. I could rip a diff apart in a few minutes.

If you really want to run the STS in the 7, buy spare parts, red loctite and some %2.5 nitro.

Throw a .21 in that buggy - you'll love it.