Sorry to make another board recommendation thread, but it's my turn to ask

First off I'm a little over 6' 3" and 192ish pounds so I'm bigger than the average dude. I've been surfing fairly consistently (2 times a week average) for about a year and a half, although there was a 4 month chunk in the middle where I was living away from the beach and so didn't surf. I started on a 9' 6" longboard, pretty quickly transitioned to a 7' 4" and have been riding both boards since, focusing more on the shorter board lately. I don't know if you would call the 7 footer a standard "funboard," but same idea. I actually had it shaped for me, told the guy I wanted something to more or less learn on but that could progress with me and ride a variety of waves. Dimensions are 7'4" x 21" x 2 7/8" rounded pintail, not too much rocker to make it easier to paddle, can be ridden single fin or thruster. Just want to give you all an idea of what I've already got. I've enjoyed the board, can only really compare it to my longboard though. I can be a bit inconsistent, but when I'm fresh in the session and feeling good I'm catching the wave, popping up fine, maybe getting a decent bottom turn and then riding down the line rather blandly. Lately I'm trying to improve my bottom turn, pumping/maintaining speed, and just overall riding the wave better with turns and what not.
So here's my predicament. I'm getting very frustrated in bigger (chest high or bigger) surf lately, and my scapegoat is the board haha. I don't want to blame the board for my lack of ability, but in all seriousness the biggest problem I have with it is it's a freakin tank trying to duck dive, especially when my duckdiving ability is not the best, but its hard practicing duck diving on a board with so much volume IMO. When I'm fresh I can surprise myself at times with a solid duckdive, other times I do enough just to get by but am not efficient at it. Muscling that thing under is work, and tires you quickly. I've definitely seen myself tire way quicker because I'm getting worked by bigger surf rather than just getting a few duckdives in and getting out back. Don't get me wrong, I get out, but I know that the extra fighting tires me out a lot quicker in a session which equals less waves caught which equals less waves ridden which equals not a lot of improvement. You guys get the picture.
So I didn't think I would look at getting a shorter board as quickly because in my mind I haven't "mastered" my 7'4", but I feel like it's holding me back in the bigger stuff. I have also wondered if the minimal rocker hurts me when the waves get steeper and pitchier. I don't think I know enough to judge, and like I said I don't want to blame the equipment instead of my lack of ability. Regardless the sheer difficulty in duckdiving it justifies to me another board for when the surf gets bigger. So I say all that to ask you all what do you think I should look for? I've thought something in the upper 6 foot range maybe since I'm a tall guy and I don't want too drastic a change and a long learning curve? I get a bit discouraged when hearing all the talk about the difficulty of going shorter board wise, any advice there? Thanks for reading and for the help guys