Here is my attempt on the first Achilles. Excuse the shoddy knife-work. I did this before reading an article where a proper circular drill was used. I wish I had such a drill, instead of chipping away for hours with a knife.
The turret needed the middle part, so I could attach the turret to the hull. I cut away as much as I dared. Should be able to fit two men in there.
I didn't want a matching bar across the hull. It would limit the turret traverse by getting stuck on the legs of the crew. This way I think I have managed to find a way where the legs won't get in the way as much, and I can traverse the turret between 90 and 180 degrees.
This is how it looks together. I am tempted to take more off the hull.