I would like to take 4 bikes along on some of our camping trips.  I do not want to drill the roof for a rack.  Even though I already have a receiver hitch rack for another vehicle, I am not convinced the Vanagon has adequate support for more than two, perhaps three bikes.  I've looked at Fiamma racks, but they only hold three bikes.  My thought is to buy a small trailer like the one below and mount my roof rack on it.  I'm sure this has been done before.  If so, what advice does the collective wisdom of this list have for me?  My main concern is the light weight and high center of gravity may cause the trailer to be unstable.   Maybe I have no need to worry.  Any thoughts?

  http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90153