I’m thinking of picking up a longboard? The problem, I don’t know the sizing? Go big for float or smaller for performance? It will be for smaller surf! I normally ride fishes in the 6’-2” to 6’-6” range and short board 6-8 to 6-10. I’m 6-2 and 230lbs … thanks in advance
If its for smaller surf, and at your size, you can hardly go big enough 
I’m 6’2, 220 and in waist & under waves I like them 10’4 to 11’ and 3 1/4 to 3 3/8" thick.
I grew up on the East coast of Fla. and Brevard and St. Lucie counties were our stomping grounds. There’s a lot of varied smallish beachbreak waves in the area, so a longboard was a must in your quiver to surf year round. Up to shoulder high I loved thick boards in the nine to ten foot range with 50/50 rails. Stepdecks worked unreal, but Noseriders are great too with the extra tail kick. Both models facilitate quick turning, especially with a good pivot fin like a DT or Bing. The old Wingnut’s work nice too. I’d go with a singlefin so the board is loose, especially if you’re coming off shorties. Hansen still offers the Master, Bing Lightweights are cool (but I miss the stepdeck!!), and I think Surfboards Hawaii still does the Model A. Matt (Bing) even does a UFO if I’m not mistaken. And there’s always the Hobie Slug or Hansen 50/50 if you want a REAL tanker. I mention these because they seem to be the closest to the 60’s style boards which, in my humble opinion, work best in small waves. But that’s me … You have a great problem, no matter what you choose, you’re going to have a blast!
go Long, narrow and thin… thruster or quad and lots of nose and tail rocker… rip the wave
lee
Depends on how you want to surf it… do you want to whip it around, or do you want to cruise and noseride?
Either way, you gotta Go Big… at least 10-0. I rode “performance” longboards in the 8’6 to 9’2 range, light and thin with sidebites, for a long time. They’re fun, but I wanted more noseriding capability, so now I’m going with a 9’3, thicker and heavier, with a 9.5 Farberow Flex Fin from True Ames, and I’m digging it. Noserides absolutely anything, but dosen’t have that quick responsiveness that the PLBs had. More old school.
So figure out how you want to ride it first - do you want to try to ride it like you would a shortboard, or do you want to ride it like a traditional longboard. For me, these days, if I want to ride a shortboard, I ride a shortboard. But if it’s lazy, small, summertime peelers, and the water’s warm and the sun is out, I’m walkin’ the mal.