Great job on the room, plants are looking much better in last pix.
I too just finished a 14x21 room with 16 foot ceilings and 10 Nanolux DEs on the NCCS system. using the r-tech panels, but put the foil to the outside and hung panda film. I was originally going to do it like yours, but you get more insulator value if foil goes out.
Gotta love hanging this stuff, so light, I used drywall screws with fender washers, then taped the seams with stucco poly film tape. Used a cordless grinder with a 5" metal cut off wheel to cut the stuff for a clean no mess job.