I run a continuous rig line with my HH hex tarp. I put the ridge line above the tarp sometimes and sometimes under it. I find if I use the line over the tarp I must tighten the corners before tightening the top and by so doing get a real nice taut hang. If I put the line under the tarp I can get a much crisper line and can get the tarp good and snug but I must have my tarp line very tight. I will be using the line under the tarp in the snow this winter, if I get the chance.
I find both work but they take a different approach.