Collar & capstan? Haven't heard of that one before. Doesn't seem like an easy knot to do on the fly in the kayak from the directions I saw.
Have you used palomar knots? I always do two wraps of the loop before putting it around the swivel. Never had one slip or bust, but I haven't fought a 1+ metre mackerel yet... I've only snagged the bottom & broke other parts of the rig. Never the braided knot.
Personal Best Yak Fish: Australian Bass 46cm, Mangrove Jack 38cm, Giant Trevally 48cm, Flathead 65cm, Tailor 37cm, Whiting 36cm, Bream 37cm, Snapper 41cm, Tuskfish 38cm