You should have had a word with the guys at Silent Planet, they would have been able to tell you which size.
Alastair mentioned yesterday he took the XL jets and he is a size 10 but wears turbo soles. I thought a size 9 was a rough indicator to XL's. I understand there is now a slightly smaller size of turtle because Adam mentioned it not long ago.
I would give
Underwater Explorers a ring and ask them.