Looks like you have already gotten a good grasp of the parameters. Fine tuning them is a matter of trial and error. Also make sure you are well balanced in DEC and that you have no cable drag.
The main drawback of the DEC stepper motor is its current limit, which is about 2/3 of the RA motor (for my CEM25P). That means that the motor is prone to losing steps if there is ANY excessive drag.
As you found out, overtightening the tension screw can induce such drag.
As for sufficient pressure on the worm gear: I now wiggle the mount in DEC while tightening the tension screw. Once I can no longer feel a discernible movement, that's when I tighten another half turn, then stop. I found that to work best in my hands. Depending on where the telescope is pointing, i.e. how much potential torque there is on DEC, I can now get the DEC RMS down to <0.5 on a good day.

All that being said, I think we have to be realistic and accept that a low end mount like the CEM25P is not optimal for telescopes with a focal length of >500 mm. I am using it with a WhiteCat (250mm focal length) and for that it is perfect.

Jo

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