I ran into some problems with my earlier designs. Squaring off the rear of the receiver would leave no room for the web of your hand.
I had not realized this and was working on a Gen II version that had a 180B style rear end. This had the same problem as Gen I but also would not allow the BRN-180 to drop down into the receiver at the back.
I started fresh this morning and left the rear end alone and just modified the front to resemble the AR-180B/Nodak NDS-18S.
Astute observers may have noticed I also modified my pistol grip to fit on a standard AR-15 mounting point. I have had this request from some of my followers on Instagram.
By the way if you are on Instagram give me a follow. I post a lot of other stuff on there that you might like. Look up BigRix, the same as my Youtube channel.