yup, we've got a local guy that can do all that.5th elements are so cheap these days you can pick one up and send it off to Avalanche and have yourself a custom-tuned(to you and your riding style) position sensitive rear shock for $300.. can't really beat that. Not sure how it stacks up against a RC4 or a Vivid, but I'd imagine something that's slightly more primitive but tuned specifically for you will perform better than something newer with a off-the-shelf tune? I don't know for sure, just some food for thought..
http://www.suspensionwerx.com/