Let me start by saying you bought a great kit. I have AM armor and love it. I was at the same point as you 1.5 years ago as far as Heavy Weapons trooper va Sandtrooper. I went Sandtrooper and do not regret it at all. As far as the backpack, remember Sandtroopers do NOT have to have one for basic approval. I did mine with none. I am going to build one this winter and go for level 2 approval. But unlike the Heavy Weapons trooper you can troop with or without the back pack! That was huge for me, and I can’t imagine ever wanting to troop as a vanilla ANH TK, so boring, lol. As far as the Mimban, they do look super cool, but, I just don’t have enough knowledge to comment, hopefully someone else will chime in.