Sometimes my typed words don't follow my thinking so let me clarify.
When I referred to using 6 and 7x and fighting a trout too hard I was thinking about big browns specifically - over 26 inches. You can be skillful, or lucky, and land one with 6x and not kill him but chances are in very low DO conditions you'll hurt him, maybe kill him.
Knowing how to fight a big fish is important, as mentioned. Good examples.
Slipping it on the gravel - if I don't have a net, I'll work the fish in shallow enough water that I can control him... not up on a dry bank. Again, poor use of words.