If you are talking about running a support horizontally across the rail which would support one end of your bed, I would not do that. If you were running a vertical support from the floor to the ceiling, and using the van rail to hold the top of the support, I think you would be ok since the weight is supported by the floor. Have you considered building a free standing frame out of aluminum channel called 80/20? I built my bed frame out of this and have storage underneath. It is a little pricey; but, very versatile.