well if you open this picture, and then the next one in the same browser and just press forward and back a couple of times you'll see exactly where an why these guitars are different.
http://www.prsguitars.com/showcase/current...s/lg_stan24.jpg
http://www.prsguitars.com/showcase/current...s/lg_stan22.jpg
I looks to me that the 24 templates would not be suited for a 22 fret guitar, BECAUSE, the 24 fret neck is longer, cutting the heel a bit short would not do the job, it would most likely lead to a loose joint, and like wes said the bridge, and bridge pickup would also need to be slid back the according ammount, although you could measure this and reset the template after routing the neck pickup and body contour, again like wes said, the whole point of getting the templtes is to start off on the right foot, not the wrong foot with a crutch
Sorry, but if it was me i'd probably wait.
Although, if you only have access to the tools for a limited time, and feel you can perform the above accuratly, then it's up to you.