I've recently acquired a LED panel to use as a background for small still life shots in B&W. I can't get my head around how to meter for the panel so that it comes out a true white. I have been using a incident meter to measure the light coming off the panel (right up to the panel face) and setting it at 2 to 3 stops above my exposure and main light. I think this might be too much? But I just can't figure this one out.

Thanks for your help.