Talk to the people at Sunstore 0845 1800 654
info at sunstore.co.uk
They were very helpfull when I was thinking about buying an 80Watt panel for my Hymer Nova.
I went back to them after a long chat with them and bough a full kit. They offer help on installation as well.
I looked into this and was advised by the caravan manufacturer not too, as the Elddis 302 has a non bonded skin.
Also contacted several fitters and suppliers, most told me it would not be a problem, but last thing I want is damp issues due to flexing while traveling and weakening the joints around the roof vents / skylights.
So I decided against it, I slide the panel on the roof when on site you can also use it at an angle for more efficiency.
Would have liked a fit and forget but I can also use the panel for other applications.