I agree 100% on your fillet method. If you just try to make a cut from the head down or tail up, you are losing a significant portion of the meat---I don't catch so many fish that I want to waste any of the meat on the ones I catch. If you try that one-end-to-the-other on a cobia or a big king, you're losing a ton of meat.
You know whereof you speak!
Also, David and others are correct. You need more than one knife---you don't try to do all kinds of fishing with just one rod and reel. At last count, I had five knives on my cart, one of which is my loaner knife which suffers all kinds of abuse, and I don't care. And my pocketknife.

