That’s awesome, I need that CAD program. You are right though kinda. I think I am actually going on the other side of that black piece. I will make a large hole though it and bolt a nut trap underneath it. I think. Considering a piece that actually spans the gap and connects the black pieces to increase rigidity a bit, maybe. If I go on the other side of the black piece it opens up the tool holder area for a closer more rigid tool connection.
The other one doesn’t have a physical trap because world wide all these dam coupler nuts are different lengths, and widths. I also need to make sure there is room for the people that will use a leadscrew as well. Really though in the beginning when I originally designed it I/we were using the flex shaft tools with almost no weight at all so that connection was overkill.