since you are doing this to a claytor and a clark, your ridgeline will need to be at least as high as the top of the netting, which is several inches higher than the hammocks suspension/end points.
i like mine outside the netting. it's easier to remove that way too. the only reason to have one inside is to support the netting (that's why a hh is inside) it might make the netting on the claytor tighter though, which you may or may not care about, and i don't know if it would even work. getting it the exact height would be the thing.
anyways, decide the height of your ridgeline. the lowest option is probably better b/c it will determine how low you can hang your tarp (on the claytor anyway). i would put it right at the top of the netting on both hammocks.
once you know the height of it, you can see just where it will intersect the support ropes.
hang it like you like it without a ridgeline. have someone else lay in it after it is adjusted. use string or something to mimic a real ridge. set it to the height you want it to be, mark the intersection point on each support rope, also measure the distance between these points (your ridge distance).
from here you can do whatever, you can use as few or as many different pieces as you like. you could put a ring at each intresection point, and use 5 pieces of line, you could tie a bight in the suspension rope at the intersection point and attach the ridgeline to that, you could tie the ridge to the trees and tie bights in it, and attach the support ropes to them. regardless, the location of the intersection points and the ridge distance you need/choose is the same, connect the dots any way you like.
for the claytor, i would join the webbing somehow to make a single suspension point at each end and start from there.
the way you chose to do it doesn't really matter unless you want it to be easily removable, adjustable ect.
just use whatever strength you use for the support ropes, although you could probably go down a few sizes if you are concerned about weight, which you probably aren't, considering the weight of the clark.
just curious, never seen a clark. do you lay diagonal like in a hh, or more inline?