I would say not, Its' for use in buildings not vehicles. It may not remain flexible, long term or be suitable for applications that move & flex. As stated above, use Sikaflex 512 which is specifically developed for caravan & automotive body use.
Professional yachtbuilders who use Sikaflex products all the time, insist that when joining two surfaces of different materials, you must use a Sikaflex Primer.
This is a clear liquid that you brush on and leave to dry. (about 10 minutes). When dry it has a sort of dull smokey look.
As they are joining surfaces that are meant to stand up to Atlantic Gales, I reckon Sikaflex will do for caravans.
sikaflex sealant 292 or 512 will be fine.you can order from CAK tanks 08707572324 or crusader products 0115973 6939.for nearest stockist call burden group 02476466461
------------- the only silly question is the one you do not ask.
You would probably be ok without the primer. As long as both surfaces are well cleaned and degreased (with alcohol but NOT white spirit as this leaves an oily film. Acetone is a good degreasing agent BUT is a solvent to ABS and most foams.) Sikaflex should make a permanent bond that will be very difficult to part without damaging the structure it is stuck to!
be careful what you use because pink grip will probably melt the polystyrene in the van walls i used low modulus silicon when i reframed and reboarded my van its now solid!
Whether you use primer with Sikaflex or not is entirely up to you, but if I was using Sikaflex in an area which, once bonded, would not be easily accessable to repair again, I would be making darned sure that I did the job right the first time.