I will not say a max test to use but 200 braid is the lightest I would try. Match your clip release to the diameter of the braid. This will determine what diameter to purchase. Test at the shop before you buy. Or add some tubing to the ends of your clips for a better grip, not to hold but to keep from sliding up or down. If you have auto electrics use something to set the stops, crazy glue, floss, or crimps.
Use 200 or 250 lb. Power Pro. You can use 300-400 lb. mono but it will have a lot more drag in the water and you will get less depth if you are running planers. Add a snap swivel at the end of the line and attach your downrigger clip to the downrigger. We use the Blacks clips (don't remember the number) but the bottom of the clip has a clip that holds the downrigger ball/planer. Everything is very compact and eliminates fancy rigging to attach the downrigger ball and/or using the cheap release clips that open when you squeeze them (the ones with the rubber "jaws"). Works like a charm and less hardware in the water.
fountain-boy this is a pic of the Scottie. The connection in this pic is using a d-link to attach to a planer line. There are two settings for tension on this Scottie release clip. The mono used here for the line is fifty or sixty pound test. You do not need the d-link but you can substitute with a large coast lock crimped to. This release has held a 4 arm umbrella and 8 0z bucks with 9" shad trolling 3 mph. When in rough waves 4 to 5 feet I have seen this release pop when the planer line pushes through a wave, not many times though. The Scottie release clip has rubber ends and max tension is used with the weight of rig described above. The clip is of a hard plastic design.