I would like to propose a little experiment. Grab your paddle and stand it upright next to you. Raise your arm up straight and see where it comes relative to your hand, wrist, fingers, whatever then post and tell us.

My theory is that you should use the proportions of your body, including your arms to determine the optimum paddle length. I think it should lie somewhere between the top of your wrist and the middle of the palm of your hand.

My paddle is a little short for flat water and it snugly fits into the crease between my wrist and the heel of my hand.

If you scour the net you will find recommendations for paddle length for anything from 4-8" above your head, or line your nose up with the base of the paddle blade. The problem with these guidelines (apart from there being so many different ones) is they ignore the proportions of your body.

I am 6'1" and my paddle is 11" longer than me and feels a little short for flat water but just fine for the surf. I think I have fairly long arms so my arms are the limiting factor for paddle length.

I would recommend that the max length is 8 inches longer than you height. Also take some time to check your technique. The sport is great but it does have a little nasty side that you may need to be aware of. That's shoulder injury. The ways to avoid it are by correct technique and shorter paddles.
It put me out off the water for 12 weeks with a shoulder inpingment. I am back on now and stoked. I am using paddle 3 inches longer than my height on a small board in the surf and 7 inches longer for a big thick board. I also concentrate on a few things when paddling. Keep your upper arm elbow down, try not to reach out too far in your stroke and try to use your trunk in the stroke more than just your arms.