The Xtracycle already has built in fender bosses! I used the three of them then added a little plumbing strapping to secure the top of the fender:
I had to slightly bend the fender stays, as they were a little too long with the snap deck. And I have to admit that the first picture above was my first attempt with the strapping. I learned that if it is too snug, the snap deck won’t snap back on. I got a second piece that was about an inch longer (adding a total 1/2 inch once it was doubled) and that worked much better.
Credit where it’s due, I did find some helpful fenders and xtracycle sites. Thanks to: