Iam about to do the same on the back of my van useing a old style bike rack that fits under a tow ball .I am going to bolt a jockey wheel clamp to the back bar on the van I only have one spare( I see you have 2 may be a bit harder) I seen photos on the Forum of a van with this set up have all so seen one with the racks fairly high on the back some one will have the anzwer for you
Doug m
PS google photos of bike racks on caravan heaps of photos
-- Edited by doug m on Sunday 11th of May 2014 06:26:50 PM
Hi.We went AGAINST advice on mounted a tow ball fix on rear bumper.Result was not good.Too much movement every which way caused failure.Now on van number 7,we aim to have a post welded between gas bottles to raise bikes and forward face.I have seen this a few times,often with front wheels removed for tighter turns.