So I recently purchased a MSI Carbon Fiber Roof. Just wanted to say that the roof was extremely well made, fit very well and was delivery quickly for install. Basically the product was perfect and transaction with MSI was very smooth.
And yes its a full carbon roof, so the OEM steel one is cut out and replaced, however, since MSI made the roof so well, you can keep the existing roof beams/structure. Thus you can keep the integrity of the underlying OEM roof structure if you choose. You can shed even more weight by cutting out the steel beams, but without a full cage, it wouldn't be a good idea.
Regardless still a nice weight savings, and a very well made roof.
Regarding cost - PM or contact MSI since I don't know what their final retail pricing structure is
Some pics of the roof installed