hello can any one help please,i dont have a roof rack and cant realy afford one,so was thinking of screwing my flamma box to the roof?i am worried about doing this,but i understand that flamma do a fiting kit that screws on to the roof and they say you dont even have to use mastic to seal the screw?the box i have is a flamma ultra 3, other than water getting in to the roof im worried about the size screws to use?any advice would be very helpfull,regards si frosty, my motorhome is a CI