Hi, I've have read various posts re towball mounted cycle carriers and fully understand the problems with noseweights. I am looking at either a roof mounted system or the cheaper option as I already have one is a rack which attaches to the rear of the car, I have a Vectra so it rest on the rear window and boot lid. It does hold the bikes high to avoid covering the rear lights, my question is does this effect the nose weight or is it only if it is on the van it's self or attached to the towbar? any help would be gratefull, thanks.