YT are pretty easy to clean. They have firm meat, fairly tough skin, and heavy bones, so if you slip a bit you don't slash the fillet in half like you can with tuna or other softer meat fish. Here are some videos to contrast.
http://www.youtube.com/watch?v=uyVA8JjdQ1g
Tommy does a pretty good job here but he does indeed trash the belly when he removes the ribs. The farther you wrap the initial shoulder cut, as opposed to a 45 degree cut, around under the head the more belly meat you get.
http://www.youtube.com/watch?v=H2rTrwW-5a4
In this vid the cutter is more prepping the fillet for sushi or to set up for cooking. He carefully removes the ribs with as little meat removed as possible.
I couldn't find a video of it, but my way of maximizing belly meat is to remove both fillets with shoulder cuts even more shallow angled than Tommy's. I can then remove the belly in one piece. I prefer this for smoking the fish. Mike