It is not my intent to start more 'flame wars' with regard to Alloycars (search on CC if you're curious), but it appears they're offering an aluminum body 'upgrade' "for FFR-MKIII owners. From February up for FFR-MKIV owners as well." Check for yourself at
Alloycars Porsche 550 Spyder aluminum replica MK5 Roadster
It appears at least one CC member has signed up for this upgrade - see thread at
Alloycars are real
Disclosure: I have no interest in Alloycars or FF.