Cast off for Tubey?

Well, as you can see, I've nearly finished the body of Tubey. I LOVE this pattern, especially being able to try it on as I go! It's the first no-sewing up jumper I've made!
Anyway, I was wondering how other people had cast off their Tubeys? Did you just use a normal chain cast off or did you use something special to take into account the ribbing? I looked in my Handknitter's Handbook (Montse Stanley) and thought maybe the Decrease Cast off, which I've used for another ribbing cast off with success. Any thoughts?