David,
I second what the other ops are saying. Just say no if you economically can. It will be near impossible to keep a steady shot with a multi-pin cable hanging off of the camera, no matter how well you tether it. This will only make you look bad, regardless if they believe you or not, and you won't be happy with your own results. It's better to tell them no than to struggle to try to get a few usable shots. Tell them you, and they, would be better off if you shot hand-held. Good luck either way.
David Wolf