I am 5'8" 160 lbs, and I can almost duck dive my 7'4" funboard. I am not even that good. You should definitely be able to duck dive your board with some practice.
Hey Arby I'm 6'0" 180 lbs and I ride a 5'8" quad and 5'10" thruster, partially for the ease of duck diving. It definitely makes a difference to be able to get out there with less hassle. However, I sometimes feel like I should be on something a little larger due to my lack of skill. I absolutely love riding my longboard but it's not worth the beating on a big day. That said, a smaller board might help you work on your duck diving technique, which could translate over to your 6'2". Honestly though I think Kahuna Kai might have it right. Time to hit the weights!
Have you tried pushing your foot at the tail of the board instead of your knee? You might be saying "of course Dumas" but you'd be surprised at the amount of people who don't use their foot to push the board down. I have a 5-8 fish cut with tri fin set up and its 21 across and 2.58 thickness. In bigger surf its tough to get under sets but because it floats great, it pops up quicker after a hold down. Thin boards tend to be held down with you in bigger waves. Good luck
Get a wave jet and plow through it like a schooner!
KK's advice on fitness might be just the ticket for you.
Or, you could consult with the njshredmachine?
Known for his physical prowess on 20' (hawaiian?) nj beachbreakin' barrelin' beasts & his specialty, body beautiful beach bench offs. Now there's a dude that could whip you into duck diving shape!
im not a very good surfer but i have always been good at duck-diving. i learned on a big ass epoxy BIC funboard when i was younger, so everything since has been slowly getting easier to get under waves. my first board i got is a 6'8 aloha RV, basically a big fat shortboard-shaped funboard, and its very hard to get a 100% duck dive without losing any ground, but with the right technique you would be surprised at what you can dive.
i start by pushing the nose down pretty deep, and following through with my knees, dunking the whole board under. i keep on the pressure with my knees while stabbing the board foward, thus putting more water between the board and the surface--since by now you should be under the wave but not through the meat of it yet. then i pull myself hard back to my board, like a reverse push up. if done correctly you should come out the other side ready to paddle into the lineup!