hi, we have one but instead of fixing it we have a lead to plug it into which enables us to park the van in the shade while still charging the batteries.
We have a pair, which werent working very well until my partner found a problem with the plug, but they are portable, like Tezza's. Just plug into the Anderson Plug, and move occasionally during the day if we are at "home" otherwise point northish! Well worth it when they are working!!
The only problem with them being portable is their attractiveness to passers by who might think they have more need for your panels than you do.
I have 2 x 130 watt panels fixed to the roof.
My only concern with you doing it yourself gitsho is the possibility of effectively resealing the entry point into the van.
Try Sikaflex 252 to stick them to the roof & make the cable entry thru the side panels rather than the roof .. if possible. Sikaflex 221 might be the go for that seal.
Some pros don't even screw the panels to the roof .. just use the 252.
Rob has fixed 2 panels to the top of our oldish Viscount with no problems. They are actuallly screwed on aluminium frames and the frame screwed to the side of the van. Wiring runs to the batteries.