This one technically wasn't an official troop, but I had the honor of being a funeral honor guard in my TD with 2 other TKs for our fallen brother, TK-92217.
I didn't even notice that on the arms until now, but I did see it at the knees in this pic from their website:
It does have the appearance of R1 armor as well.
Obviously, the game hasn't come out yet but allegedly this was a leak from an advert for SW Hunters game that is in development. Kinda cool to see this weathered trooper!
You are on the right track with that spacing. Will just have to put in some scrap into it and then polyflex (I love polyflex) and build up and you should be golden.