You don't have to, no. Structurally, a roof skin really is nothing. I've got my original one in the garage, and it's just a really thin, flimsy piece of steel that can be depressed with your little finger. It's just held onto the roof parts that do really matter by a series of spot welds. Personally though, I'm not sure if I would want to fit one if I didn't have a cage, just for peace of mind. There are plenty of cars in the world running a carbon roof skin, which will have been stuck on with Tiger Seal or similar, because that's all you can do with it really, and have seen them do 180mph+, and still not budge at all. But, whilst if I decided I really wanted one, I'd probably still have one regardless of whether the car had a cage, I know I wouldn't be so confident as I am with a decent cage. As things stand, I didn't think twice. fair enough i was just considering something like that for my escort 3 door project i have, as it currently stands it doesn't have a sunroof so i was considering putting a sunroof in, but when i saw that beauty carbon fibre one you got, that made me think twice for definate!! If you're just wanting it for cosmetic purposes, then I'm sure you can come up with ways of adding extra security. Considering a standard roof skin + sun roof will weigh over 30kg easily, and a carbon fibre skin is around 3kg, I'm sure you can devise some form of extra security to the roof and still save weight over a sunrof skin.