Eric has an excellent point that, because of the structure of the truss fork, there is definitely some extra support built into the design of the fork. That said, I would recommend that any sort of bag be of a small-ish diameter (say 6" or less), for as the diameter grows the bag will move forward away from the the headtube of the bike, as it will not fit into the triangle created by the forward arcing trusses. Most of the commonly available handlebar bags rely on some sort of strap around the headtube.
The pictures above (with all the CDW gear) demonstrate this point quite well.
Scott