Fin said:
"Do any of you have an opinion as to whether this is a significant concern,
or that the effect would be minimal."

I think the bikes will be more protected from road debris on the rear.  The
bikes will be dirty either way, but up front the thrown-up stones and tire
chunks will damage your bike as well as your van.  Why damage both?

I carry mine inside, but that's me.

Bill Marshall
85 GL Tiico "Pandora's Box"
Aurora, IL