Best board size for cable

Hi guys, I'm looking to buy a board to use purely on the cable, I'm 5,10 and about 160lbs. Just wondering if anyone can weigh in on what the best board size would be for me, I've ridden boat for the past 3 years on 138s, but due to a change in circumstances I'll be riding a lot more cable from now on. I'm pretty sure I've found my perfect set up (2014 Ronix District Park), but i don't know whether to go for a 134 or a 138. I like a mix of big hits off kickers, to pressing on sliders and I want to learn some air tricks. So any advice on which size I should go for, and even board recommendations would be appreciated.
Cheers, Alfie.

I'm 5-7, 140 and ride a 138 on the cable.

138 is almost too short for you on cable IMO. I am smaller and ride a 139, and it feels too short nowadays, thought it was too long when I got it. With your height and needing some widened stance on ya, I'd say 142 range. The cable boards are flexier so your weight won't really be as much of a factor, and it gives you more tip and tail for obstacles.