All the meat from a yellow tail is good to smoke. The bellies and collars are preferred due to the higher fat continent. They don't tend to dry out. While the fillets are more versatile for many other cooking methods. This video isn't of a yellow tail but it shows the shoulder cut and one piece belly removal. I use this exact technique for tuna with great results but haven't used it on YT.
http://www.youtube.com/watch?v=0hvAfQqWAL4
When it comes to fish handling and processing, if the Japanese do then I should too. Mike