I added a 26t Salsa small ring to my 2005 CrossCheck complete. I just got a 2.5 mm spacer (it had the effect of putting a 5mm wider BB in).
The spacer shifted the rings out just far enough so the 26t would fit.
Read my posts at bikeforums.net
here (I'm hopperja on bikeforums.net)
I've got around 4,000 miles on this setup and it has worked fine since day one. Chainline hasn't been an issue, as I originally thought it might. I'm still using the stock chain.
note: I replaced the FD with an XT FD-M761, as the stock FD doesn't have the range needed to move between all three chain rings (or so I thought; Ben's link above says otherwise).