I have done this on a couple of vans to accomodate the Fiamma Caravanstore
If you remove the light and drill another hole for the cable so that you can lower the light so that it still covers the upper screw holes this was enough for my van.
If you need to lower it more you can cover the holes with screw caps or a long white reflector.
On our present van the roof is long enough to travel with the caravamstore to the rear of the light and then its just slid forward to the stop in use.
Hope that helps.