I made this to use the least amount of hardware. Works with 2020 extrusion. I got the threaded rods from the orange big box store. The rods are 5/16-18 threads as is the printed holes. The threads are snug fit. I put the rod in a vise and used a 15mm open end wrench to thread it on. Since the threads are 5/16 which is very close to 5mm, that could be used until it threaded tight. (untested). Nothing has to be disassembled to install. Use 4mm cam type nuts with 4mm socket head screws or use a washer under a different type of screw if needed.

I thread the top part first with the whole rod and snugged it up at the top. Snugging the bottom part where I want it next. I laid the rod next to the bottom part and marked the rod about ¾" or 20mm past the thread hole on the bottom part to cut the rod. Take both parts from the frame, cut rod and clean up end and thread the bottom part on. My length was about two feet. Square up parts to the frame and bolt on. Do not tighten to much or the screw could pull into the infill area.

I used a generic PLA with three walls, 0.20 layers, 25% infill, no supports but I did need to clean out the bolt mounting holes.

It did help improve printing but has limited Z axis height. I never used the printer at full height, so it was not a concern to me.