Had another thought could you? and this is only a thought not use the adhesive studs and use the Kampa Limpet System instead?
Morphy

Hiya Colin I would not use the adhesive Protec at all the Kampa Limpet use suckers there is no need to use or there would be no need to use the adhesive Protec studs. If and I think they will be strong enough when traveling due the pressure pushing them to the van and not away.

If they do work? there will be nothing stuck on the van at all as you take the suckers off when you remove the Protec and stick them on when you put the Protec on for travelling. Morphy