We have a few of those kits laying around also.

http://oi58.tinypic.com/52zakw.jpg

Never actually installed one because they are rather bulky and stick out like a sore thumb.
I would imagine that they would be easy to break off if you are loading or unloading anything big into the van.

I prefer to use a standard truck dome lamp mounted in the rear load area as they are flush with the roof and have a cleaner look.
http://oi60.tinypic.com/1z4gvaf.jpg

Things are a blast.