In reply to BernieMac:
One drunken night many moons ago myself and a mate played golf off the roof of my old van into Dunbar harbour in the early hours of a party at his house. Great days!
Less great, was the leak the van developed the next time it rained hard.
Whilst the roof itself (the metal) dealt well with us prancing about and scudding the roof a couple times with the club, the bit that created the leak was the bonding between panels. Repeated large movements of the panels weakened/peeled the bonding apart. Fixing with silicone didn't work as it still needs a bit of flex (not sure what they use in the van making factory in the first place?). Ended up going for duct tape, then silicone, then whole lot sealed with vinyl. Not pretty, but it worked!!
My advice? Stay off the roof if you can.
So close to hitting the far side of the harbour too....