Rope makes sense. Did you find it stretches therefore loosens some? Did you pull it tight with a come-a-long? Be careful of predators digging under the bottom of the fence. They try it here all the time. We put wire attached to the outside bottom of the fencing letting it lay on the ground going out 2 to 3 feet. It could be buried some but whole idea is when animals dig to go under they will run into the wire and be unable to continue digging through. I have 4 holes on one side of our pen where something has tried to get in that I need to refill. They got to the wire and were unable to proceed. I have the other 3 sides covered with large rocks....haven't had time to cover this side.
Be sure and place a roost for them nights when locked in the shedded area with platform for their feet being at least 4" wide so their feet don't freeze if you have cold weather. I had to do more roofing on our pens. We have two 10 foot logs in each pen. Only one was beneath the roof and I'll be darned if they didn't choose the uncovered one nights in rain, cold, freezes and even snow. Could have removed that one but I feel having other places for them to stand is like having a larger pen in a way. We built corner nesting boxes 3 to 4 feet off the ground and it's amazing how much they use them to lay during the day and still use the ground beneath so once again we added more room for them to range in. Mine prefer to be beneath a roof but figure they are better off nights with one keeping them sheltered. 20' of the 30' depth of the pens have a roof with 10' open with only the 2 by 4 inch welded wire.
Happy I saw your pen......have some ideas now of using rope. Thanks.