Oh no...here we go again.
1st, where do you surf? reef's, point breaks, beach breaks? Blacks?....or some backed off mush ball? All this is important. Surfboards are like golf clubs, you shouldn't use one club and play a round of golf.
Here's the deal, bigger boards will get you into the wave faster, and will be faster down the line...longer radius turns, cover more ground, good for big fast days. Big boards made for big fast days are a poor choice for small days..i,e, out run the wave, getting way out on the shoulder. Bottom contour is critical, big fast days need to have the water running down the center of the board and out the tail. Thicker noses, thicker tails paddle power
Shorter will let you take a more critical drop and put into a hollwer section faster, shorter boards are easier to man handle, i,e. stalls, bigger gaffing slashes. Shorter board, shorter arch of turn, more work, less ground covered. flatter bottom contours let you sheer water off the board bottom in more positions of the wave, i.e. redirection. But shorter board on big days equal wave running you down.
So depending on your waves surfed, your board will vary...and should vary. Short peaky drop two turns and out waves. Or drop, cover-up and out, will call for a short board. Longer lined up waves with a huge wall will be better handled with a longer board. More turns per foot, or cover more ground? your call.
As for your size board and lack of rocker? WTF your 6'2" and riding a board the same size. Pretty much a death wish for the average surfer. The guys on better suited boards are catching waves on the outside, bottom turning and throwing water in your face before you get to your feet.....right?! If that was the case, then everybody would be surfing 5'6"-5'10". Look at the equalized volume of the board you are surfing compared to a average sized surfers board? Now take that board and steep it up 3-6 inches on a bigger day...get the picture?
I'm not going to get into recommending a size and shape of board for you, because everybody thinks their size and shape it the best. Hey, I'm your size, a bit heavier at about 200-210, it took me years to figure it out........We all can't surf Kelly Slater's little 5'8" board. I'm guessing your in your teens to early 20's or so. I used to think my 6'2" was the best board ever....then it was my 6'4", then it was my 6'6"...then oops God forbid I't was my trusty 7'0"....and you know what they all surfed great, just different. The more experience in heavier days will shape your opinion on what a board should look like.
All this advice will be challenged..it always is. But unless you surf like a pro, and have sponsors (I could have been a contender back in my day....I had skills) Lose the fish on big days, go to a tri-fin or high performance quad (not a quad fish). But then if you surf like a pro, you don't need advice?
Make a bunch of boards and experiment, you might be amazed there big man?
I'll crawl back under my rock with my bigger board.