I redesigned the round knob so that the screw goes in deeper and sits inside the cap more firmly. I also needed a longer M3 screw than the stock extruder had. I used an M4x12 for bearing axis. It's now installed on my Ender 3. The extruder was slipping with the stock spring and skipping when I just used a spacer. With this adjuster, I was able to get it where it neither slips nor skips and the printer seems to be printing very nicely now.
5 top/bottom layers, 3 outlines, 50% infill in PrimaSelect PETG. Printed on my Wanhao i3 with Flexion HT Extruder.