A way for you to know for yourself. See if you can try some of the boards ( or similar ones) you are thinking about, go to a surf school and try some of the boards in the range you are think about. Don't just rush to buy the first that comes to you. Post a picture of the board, there is more to a board than measurements. still think something 7'6" would be better.
I've taken up troll hunting just for fun, instead of a rifle I'll just use a pun! 冲浪爷爷