safety chain

pretty new to chaining anything. For my grade70 chains i dedicated to my tractor's trailer, i bought 'locking' style clevis grab hooks because it makes setup a tiny bit easier (no dropped hooks before i get it snug), plus theoretically in a "bad event" where there was a some momentary slack...

Looking to add a safety chain to my PJ dump trailer tractor combo. I have the trailer hooked to the flex point #FPHS 3 point hitch which makes it easy to hook up and drop the trailer easy from the cab. I only use this setup on my property. I am looking for ideas on how a safety chain could be...