If you decide to stick with metal clevises, make sure to at least use the folded ones. Ever seen a silver streak pre tied double willow harness for casting? They use folded and its gotta be at least 35-45lb test flouro on em. Thick stuff! I cant even count how many hogs weve brought in on them without replacing anything. Even when the line is stretched out and knicked, hooks are bent and showing silver areas from teeth marks, they still continue to bring fish in. The fish could care less about the 12" of thicker line, hell we even get em just the same when using coated wire.
I buy and also tie the harnesses only 12-14 inches long, so i use leaders. In most cases theres no need to make harnesses 6-8 feet long. They go on and off the roll much much easier when they are 12-14inches. And if you think the little snapswivel connecting the loop end of the harness and the leader is going to scare fish, your wrong imo. Another advantage of this setup is that if you get a knick on the leader, you just change it out. Theres no need to re-tie or change the entire harness, because its not all one piece. That just how we do it, and im sure others here despise this method, but it gets us fish just as much as the next guy. Each to his own.
Get the black clevises with the nipple if your looking for changeable. 90% of the time when you lose a blade its due to angler error. Most of the time fish will shake blades when there head comes above the water, and/or when they are in the net. The rod man needs to give the net man some slack once the fish is in the basket, and the net man needs to be relatively fast and aware with what hes doing. Dropping slack is the biggest thing imo. And keep that fishes head down till he hits the net. We used to lose a lots blades and fish when skiing them in. Sometimes you dont have much of a choice, but you just do what ya gotta do. Even the best of the best of the best drop fish, its just a part of the game. When i get big fish on, i just automatically assume that they are going to spit the hook. That way when they do get off, im not as dissapointed, and when we do land them, i get more enjoyment. Sounds stupid, but thats how i deal with it lol! Probabaly a little more info than you were looking for, but im feeling generous today!