What I have done in the past (with the best results, at least for a freewheeled singlespeed) is to figure out if there are any magic gear combinations that will work on the CrossHairs without a tensioner.
Use this site as a start:
or if you want to, you could have a rear wheel built with the White Industries Eccentric Hub. I have an old Fat Chance built up with one and it works great as a fixed/free bike.
I ran my old 29er in a magic gear combo for a year with no issues. Just depends if you can find a workable combination with the chainstay length you have to work with.