Quote Originally Posted by HoolieWho View Post
What are the precentages for slotting forbidden materia?
It actually depends on the total value of the materia. For example, a 12 str and 12 str (both tier 3) will have a higher chance of success than a 12 str and 13 str. Similarly, pushing one up to tier 4 lowers the chance further.

Middle of the road tier 3 + tier 3 is around 25%. When I tried to 17 vit + 12 vit body it was 18% (and failed). Apparently, better crafting gear also raises the chances. I'm not a crafter so I haven't really played around with it at all.