Glad you came up with a solution. The ladder method sure does have it’s Ups and Downs :o
I think it was Craig Sheline (sorry if I spelled that wrong) that had major sag issues with the material used on his first attempt a few years ago back on MLS. I don’t remember what he ended up doing to fix it.
I just had a major sag problem last Saturday when it was 111, the first of the ladder I installed off the in ground track work was not supported properly and I had to install more vertical supports, I now have them around 18" and that seems to work, what sucked was I had to get out in the heat and level everything as it would have set when it cooled off, Lot of trips in and out of the pool.