So can anyone please elaborate?

I infused Heavens' eye materia I (HEMI) 8 times now. I think the succes rate dropped to 90% after the 7th, I'm not sure. I was under the impression that one could upgrade with the #2 variant of said materia after the 8th infuse. Do I need to meld HEMI until HEMII is available, or am I missing something?