No I've not gone into fine calibration yet, my last cube was 19.7mm, which is close enough whilst I get other bits set up.

For example, I installed those spring arm extruders yesterday, tried to do a print today and the bloody thing will not extrude. It wont even feed the filament.

It goes in, it starts to extrude but then a second later it just stops.
I think it may be a tension issue, but the only way I can think to increase the tension would be a longer stiffer spring.

i did get a print to start by pulling the arm up myself, but then the stepper motor started clicking as if the nozzle was jammed, but it did extrude.
At least for a few minutes before it stopped again.