working on it, let me know any feedback. i still need to go for the dovetail. I can´t understand clearly what you mean with the cover of the caps. The holes for the threads can be modify, here we usually use metric ISO, you use ANSI? you want a hole, or the hexagonal shape? or is a mix between both? any sketch by hand could be very helpful for rectify the design. let me know any thing. Greetings.