So I think I posted earlier on about printing on polycarbonate, but before putting down the plate sticking a sheet of tin foil down to auto mesh bed level to - I found that over time the polycarbonate warped which made printing difficult. I’ve recently purchased one of those steel plates with magnets.
It works pretty well, I wire up the endstop to the MK8 Extruder (Well, twist a bit of wire over the fan grill) and then I clamp the other wire between a bed magnet and the steel build plate, then I run the G29 mesh bed leveling command it and maps out the entire build surface to the steel then you save it - there is no need for offsets cause you just twist the z end stop up a teeny tiny bit and put down your PEI sheet (Remember to remove the protective cover…that was my big mistake) and then your first layer should go down perfectly.