I use 3 swivels. I’d like to hear more thoughts on the subject. Maybe Mark June or the like could chime in!
I have used countless set ups over a trapping career of 50 years and commenting on setups is in some ways like commenting on someone's puppy. No matter what you say, or how you say it... that person's puppy is the prettiest, brightest, most well behaved puppy they, you, or just about anyone alive today has ever seen

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That said, my two cents are free, so may be worth that much!
Longer chains and rigs and shock springs were a device answer to staking set ups used in the heritage history of us trappers, namely re-rod stakes, cross staking, etc. Big gear, bigger traps, heavier operations. Been there, done that (for decades).
Advances given us by very innovative manufacturers mean lighter gear, better efficiency and productively and thus;
You can go with cabled stakes (lighter, quicker, perhaps cheaper, disposable if needed) and thus less chain and certainly no need for shock springs which serve "little" purpose for a tugging animal vs. yesterday's flopping on feet and feet of chain animal caught in a trap.
I use stock chain and swivels on the factory 550 OS 2-coil and have all over America for the past 9-10 years. Love 'em. Own a pile of 'em. Fur line - ADC work - they perform.
I use wax dirt when it gets chilly and that's as simple as you can get.
But now understand, I DO NOT CARE to work on traps!!!!!!!!!!!!!!
I love picking up turds and finding tracks.
Outdoorsy stuff. But some like welding, cutting, torching, bending, rigging.
We need these types of folks to invent new things for folks like me who don't like inside work.
Short chain, mid-line and end-line swivel and HD D-ring on the base plate (center swiveled) and you're good to go.