There may be some variation in terminology. Check stays are typically much lower on the rig than back stays. In my set-up, I have a single adjustable back stay. My running back stays attach above the 2nd spreader where the stay for cutter sail attaches. When using a spinnaker in any kinds of winds or sea state, I use the runners to limit pumping. I have done this on my previous boats as well as some of the race boats I sailed on. As for the winches, I like to have a full head sail before i douse the spinnaker to depower it. That means my primary is for the head sail and my secondary for the spinnaker sheet/guy. So they are not available for the running backs. I have a friend on here with a 54. Maybe he will pipe in on his set-up as he cruised it extensively. The rig on my boat is pretty beefy and maybe runners are not needed, the the spinnaker is equally large.
Thanks
Shaun
Okay, now I understand better. We were close on terminology, I only call 'em backstays if they go to the masthead and what I call checkstays attach, as yours do, where the cutter stay is. Anyhow, I haven't needed them sailing downwind under kite or poled-out headsail. These roller-furling masts are so much stiffer than anything I ever raced with, the only times I set up the checks are when using the staysail (cuttersail). I've only really used the checks in anger once that I can recall, when I had to sail to weather in about 45kts true. I used the staysail and a scrap of main and cranked on the checks to keep the staysail luff from sagging off and the boat pointing high.
I don't imagine it will take much tension to stop mast pumping downwind, so your 4:1 should be fine for that, and for upwind you can always throw the 4:1 tail on a winch if you feel you need more. (Just don't rip the toerail off).
Fair winds,
Jeff