What size single fin for 6'6 wooden board?

I'll be shaping my first wooden board in a few weeks, pumped for it.

Dimensions will roughly be 6'6 * 20 3/4" * 2 3/4, around 43 litres. It will be used in pretty fat waves at point breaks. I'm unsure what size single fin I should go for - would 7" be alright? Also, would this be better with some side bites?

Does anyone with some experience with single fins (or similar boards) have any suggestions? I'd appreciate any!