Hi,
could be that the cage listed on the Heigo site is not fully FIA, but i would ask them, they will add you the required bars they know what they do. Was the same with my GTA cage. And there was also a problem, that the rules required to laminate steel plates to the GFK to reinforce, but after talking to them they modified the mounting sections on the cage "feet", so i just had to bolt it in. And they re-certificated the cage, so they are really helpy, that is why i recommend them!
Take care that there is enough space for your helmet!
Heigo does it very precise and very close to the chassis- body work.
Chris