Can I stop shadows on StaticShape? (T3D)

I have a simple box model - invisible - to stop the player travelling where he isn't allowed.

Initially I made this a TSStatic, with decalType set to none (which I did to stop shadows appearing on the invisible shape).

Then I wanted to move the model (away from the player - so the invisble barrier moves). I could delete the model & recreate in a diffrent posoition - but if the player is pushing against the barrier at that point, he moves through it in the small gap when the model isn't there. So I changed the model to StaticShape & simply changed the position.

Everything now works fine - except I get shadows on the invisible model.

Is there a simple way to stop these shadows - I've had search of the help & forums, but I can't find how to do it.