Short answer: That is not a supported use.
(in other words, do not expect it to work or expect any help)
The long answer is that it will work just fine, as long as lighting conditions are within tolerances, and the "target" does not move around much. We have done this on several occasions, as have many of our users.
That being said, the whole advantage of doing this would be having an interactive "target." We are looking at a possible solution, designed specifically for force-on-force, using some technology that has become available in the past couple of years and a little bit of unicorn horn and pixie dust. Seriously though, we have some pretty cool ideas for how this could be accomplished with fully-mobile target(s) to allow for role playing and force on force. That project is pretty far down the list, so I wouldn't hold my breath.