I'm not gonna lie I just saw your post and read it from when you started last year and it honestly started getting me nervous for my build haha. I'm doing the exact same thing ROTJ SE Fett and the majority is being done by Bobamaker, set to be complete this December. I've been waiting since July last year. The thing that got me most worked up was hearing your issues with the jet pack. I can only imagine how your senses ramp up when your next to hundreds of people in public and sit back thinking "I'm literally wearing 6 grand right now" it's just nuts the paranoia must go through the roof haha
Just in time for Christmas! You are going to be so happy when you open up the cartons. I look forward to a fellow SE!
The jetpack issue was resolved with several solutions; move the collar stud placements on the back armor to close up the gap, change the shoulder straps to a sturdier canvass material and sewing them down instead of using triglides to eliminate loosening due to movements, waxing the harness bar and the surface around the clips on the jetpack to allow smooth transition, etc. This part of the costume, as most members here will testify, is the most tedious part of the whole set up. Marking out the positions requires precision, patience, and some inevitable trial and error.
All the best with your build!