As its a fibreglass roof I would fix a slim wooden batton on the inside to keep the rail secure
I agree those stand alone awnings are ideal if you intend moving the vehicle, I've been checking both porch awnings & stand alone types out but getting one for the right price has been the hardest part
I've aquired a full size awning (borrowed from family) just to try with my van but i've not attached the fixings yet either as tbh i'm trying to hold out for a smaller type such as a Fiamma/Ormnister canopy/awning but those things are pricey
