Board size, rider weight, water temp and board speed

So I'm riding a Ronix Code 22. I think it's great, BUT when the water temp drops below 65-70, the board seems to drag like crazy, as if I was pulling an anchor - my hands and arms hurt like crazy when I ride, and I get so much line tension!

I realized the other day that I may have gone too short on the board. I weigh around 180-185 lb and my board is a 138. According to the size chart I prolly should have gone with 143.

So is there a link here between water temp, board length, my weight and the board's perceived speed.

I'm thinking hard about selling the 138 and getting a 143. Should I get a noticeable difference?