Did you talk to Will or Jason?If you are in contact with the guys at Chemistry I'd email them with your height/weight, the waves you are surfing and see if they have any recommendations. With a popular model like that probably have a go to fin or at least a general recommendation as far as a more raked or upright fin.
They used to have a set of Mediums they made through Capt. Fin that I never heard a bad thing about. Looks like they're no longer available.
I like AM2s