Many in the forum use a slider to adjust the position of the camera (to focus). A 42mm helicoid is very affordable (on ebay). The focusing with 8mm is extremely critical, don’t know if it has stability implications.
I also ordered this one to try it out. Same seller has a larger one also.
PS. another option is a slider like in this built. I took a part a 3 way slider, and it was a bit unstable. This one looks a bit better (single axis). There are also multi axle ones that are very precise (and pricy).