SUP fin box position

Hey Guys

Quick question

My 11’6" SUP is ready for the fin box install.

Be running it as a single fin.

Just wondering how far up to install it and what size fin should I use.

Will be mainly for flat water/beginner and maybe small knee high surf once I get the hang of it.

Can’t wait.

Cheers

My SUP is a single fin, I put the 10.5 inch box 7 inches up on a 19 inch wide tail. No side bites or other fins. I use an old pivot fin, the same template I use on my 10’0" log.