I am 5' 9", 180lbs and had a 5' 6" Plasmic.
I love the Plasmic, it was my favorite board. The board is addictive in its looseness, speed, and size. It is super fun. I really liked how it accelerates in the whitewater and gets you back into the pocket. I haven't noticed this quality in my other boards.
Owing to this, It was quickly becoming my DD, and was surfing it in bigger and bigger waves and then I broke it in high winds, big surf over the holidays. I jumped a wave, and the wind threw it back under me and my body landed on the fins pushing them through the board. I was so bummed. As soon as I got to my truck, I ordered a replacement ASAP.
Owing to impatience of waiting, and surfing longer boards with more volume, I was debating 5' 7" and 5' 8" they had in stock over the weekend. Of course they sold out immediately while stuck in analysis paralysis - haha!
I think the board can go in a lot of different directions and be fun, hence me considering sizing up even more.
I do trust Matt. I now have 3 boards from him all very different, and all super fun. I send him diatribes of my surfing, what I am feeling and not feeling, looking for etc, and then trust his recommendations.
Good luck and have fun with whatever you get!