wow thats some meticulous data. how did u measure all that down to fraction of a mm?
this light isnt designed to run 21700 they are too long.
I bought my FT03s (sbt90.2) last month and run Samsung 40t without a problem, springs not crushed battery now dented, also run p42a as backup battery.
My ft03 I bought this March and tried to put 40t in it, no problems. Although I run efest 26650 4200mah in that usually. The different springs was something I never noticed and wasn’t aware of
It looks a bit wobbly, but the results were repeatable and I would say reasonably accurate!
Set the probe on the circuit board then zero the gauge and work out the compression by watching until the spring coils touched.
I would expect the springs vary by batch, some will fit 21700 fine, some might be tight. From my own measurements I won’t be using a 21700 without the longer tube I’m making for it.
damn, that is some professional setup