You're in luck... I just bought a Crosstrail a month ago.

Mine currently has 700c x 45 tires and I picked up a set of SKS Chromoplastics fenders (50 wide).

It wasn't pleasant putting them on due to the crappy instructions but they fit just fine (actually only the back is installed... since only one side of the front fork has threads to screw the stays onto- I need to pick up some p-clamps or loom clamps for the front fender, but aside from bending the clamp to fit snug around the fork it should be an easy install)

Beyond that, for the back fender there's plenty of clearance all around. My bike is an XXL so it's perhaps a bit bigger than yours, but I would assume that thinner Planet Bike fenders would fit fine too.

(Here's my thread searching for recommendations/solutions regarding the front fork & fender...
http://www.bikeforums.net/showthread...r-front-fender!)