That's the one. Thanks Brad
BTW for anyone else checking this procedure out. You absolutely do not have to turn the boat upside down, someone wasn't thinking very clearly here, turning a 21SE upside down is quite the project! I've done the job with the boat on the trailer, no problem. Just get the hull high enough off the ground so the board clears coming down all the way. I just drove the trailer up on a ramp. While you're at it Dyneema 12 works great for the nasty abbrasion the c'board lines get treated to.
Also be sure to use the Hobie Stainless springs. Cheapo plain steel springs last two years and gone.