Well, as hard as I tried to leave some wrinkle in the liner while placing the boulders, I was just out inspecting everything, and one of the walls (under a cascade) is being pulled taut, by I guess a boulder downstream from the area. Must have happened when placing the boulder and it slid downward a bit, taking the liner with it.
Yet another thing I can't "un-do" now. Unless am not thinking clearly, the only thing I can do now is to make sure as I build the wall on that area with rocks, that I don't try to push them too far into the wall, which would then actually stretch the liner. My plan is to place some medium rocks along in front of the wall a bit, the find some thinner ones I can slightly lay back towards the wall, then lock in place with the spill rock above. The liner would still be taut, but hopefully not stretched to the point of failing.
Man o man, like
@GBBUDD said earlier, I am indeed trying to build a Bentley my first time out (it's actually my 2nd time out, as I have built a smaller waterfall and stream some years ago), and now it's starting to bite me on the a**! Yet, no turning back now!