I would suggest foam sheeting on top of the plywood and then glue cork or homasote for the roadbed and then lay the track on the center of the roadbed.
Cool video Pual, man looks like the MOW crew was and is busy, but all for the better. If thats not determination for better Op sessions I dont know what is.
Great update and fixes you identified! My question is HOW did you isolate the #4 turnout as the culprit and switching to a #6. As I watched the video it didn't immediately occur to me so definitely something to add to my memory banks for future use lol