Pitt,
That looks better. I think that piece will be fine using the printed material. So in the front lower piece it looks like there is a bulkhead that the battery mounts against. I still think there can be some swinging if the lower frame in back by pixhawk. I might suggest a bulkhead in the back that would help stiffen up that lower frame. It doesn’t have to be a solid piece, just some way of stiffening the lower frame from swinging. Triangular pieces glued in the corners?