Fish Surfboard

Okay so i longboarded (8ft) and i could stand. I can also stand while wake surfing and for as long as i want. I got a 6'2 shortboard and i can stand. Its not that i will get up and fall, but i wont be able to get my feet in the right position to stand. So i want to get a fish (several people have told me to buy one instead of using my shortboard). What should the dimensions be? A tri-fin fish.
I am 150 lbs, and 5'8.
Is this one good for example?
http://orangecounty.craigslist.org/spo/3916568978.html
Thanks,
Aaron
I am 150 lbs, and 5'8.
Is this one good for example?
http://orangecounty.craigslist.org/spo/3916568978.html
Thanks,
Aaron