Trojans, it's VERY easy, totally DIY. Credit goes to the Turner forum. Here is the thread:
http://forums.mtbr.com/turner/dw-5-spot-rp23-mod-503070.html
Since my plastic was thinner than he had (I believe mine was 0.9 thick instead of the 1.2 he used), I compensated by increasing the size of the shim. My dimensions are such that my shim is just below the air vent hole from the main chamber to the XV chamber. Basically I calculated what was needed to reduce the volume by the same amount the Turner thread suggested.
EDIT: Here is the thread where I had my shim dimensions:
http://forums.mtbr.com/intense/tracer-vp-rear-shock-set-up-774578-2.html#post9228473
What I like better: In 5.5" travel mode and full XV volume, I felt that the bottom-out was pretty harsh/noticable, and also a lot more frequent than I would expect given my weight and the fairly mild terrain we have in my area. More air would have helped this, but I was right around the 30% number for sag, and I know that the VPP likes sag in that area. I'm coming off a 4.7" bike that had a very soft bottom-out feel - I never knew it bottomed until I checked my sag indicator. The Tracer wasn't like that when I got it. For reference, I'm around 155lb with full gear. When I shimmed the bike, I then noticed that the bottoming was a lot less frequent and much softer than before due to the more progressive ramp-up of the spring rate with compression, but the rear end still didn't have that really nice "erase the big inputs" feel I had on the Lawwill. (Note that you'll have to reset your sag - you won't use the same air pressure with the reduced volume shim in there.) Finally, I changed to the 6" travel mode and found EXACTLY what I was looking for. I like a plush, endless-feeling rear suspension that soaks up everything, and that's what I got with the shim and 6" settings, now running 135 psi (ran 105 psi with the unmodified RP23 and 5.5" mode). I was seriously looking to get a CCDBA if this didn't work, but now that I have this setup, I'm saving the money for other things. CCDBA will be a "someday" item, perhaps on a Tracer 275, but for now, I'm happy with my setup on my TVP.