We cut up another perfectly good prototype. It wasn't quite as painful given that this is the lid from the previous unit we sacrificed but it still stings a bit.
We really wanted to see how the film behaved when the tray was full of liquid. The easiest solution was to cut some windows. This allowed us to watch the film while filling, agitating and draining the tray.
Turned out to be a waste of a good lid. The film hold down tabs performed just as we hoped. At least now we know.