i have mine suspended from the roof,i have a peugeot partner,i used two sections of threaded bar from BQ,bent them like a hook,i used threaded because the roof support bar as pre drilled holes in them so i was able to screw them in,then bolted them either side of the roof support,i had to drill two holes next to the existing holes to get my fingers and the washers and nuts in
i have also placed a large section of wood against the tank which houses/holds the pump and controller and just above these i have placed two 22 mm pipe clips,the type plumbers use for piping,i then swing the reel backwards and insert the base of the reel into the clips,this stops it swinging and holds it place nice and tight
it makes life a lot easier when winding in