I just did a 400 hour rebuild on my squishy 4 year old Reverb B1. I followed the instructions in the SRAM guide. My only issue was when I removed the o-rings from the inner shaft piston there was no corresponding new o-ring in the rebuild kit. So I had to put the old o-ring back in. I have looked at the kits sold on-line and there simply is no o-ring that matches the inner shaft piston inner o-ring. Since I reused a previously removed o-ring, I don't know how that will affect the operation of the seat post, but so far, the squishiness is gone and the post operates as new.
I would like to know if you had the same experience and how you resolved it.
Thank you for your helpful post.