I think that you will be fine.
I have a large eye bolt in my training room that I have a TRX suspended from in exactly the way you describe. I am not sure what it was rated to but i stress tested it by adjusting the TRX so that I could hang by entire body weight off of it so that I was just a few inches off the ground over a mat. I proceeded to shock load it repeatedly and the hook didn't budge.
Most TRX exercises use only a percentage of your body weight so I felt that by shock loading it with my full weight I was stressing it significantly greater than I will when I train. To date it still is working fine.
If you are concerned there are a few ways to put something up that will be bomb proof.
1) Buy the "X" mount available on the website that is designed specifically for this. This is your best alternative.
If you are feeling more "do it yourselfy" there are a couple of other options
2) If your beam is exposed drill a hole through it and use a "U" bolt or thread chain or 7mm climbing cord through it to provide you with an anchor point to clip into.
3) Screw in an additional eye bolt to back up the first and equalize them using chain or 7 mm climbing cord that you can get at REI.
As I said I think that you will be fine but there are some other alternatives for you.