EMC, INI , MIN_FERROR and acheiving maximum accuracy

hi!
I've recently runned the spindle of my old gold hurco milling machine
which now has EMC with STG-II as machine controller.
I just now have made my spindle running. and i have cut some
circles cut on a wooden log. now I want to super tune my EMC system
so that i can have maximum possible machine resolution available.

Here are some of my machine settings:

MACHINE resolution = 0.03 mm or 0.001 inch (as depicted in machine'
smanual)
Encoder resolution = 200 (lines) x 4 = 800 counts per revolution

lead screws of my machine take 5 revolution for 1 inch

therefore i have in my ini the setting of INPUT_SCALE parameter
to 4000. (INPUT_SCALE)
MIN_FERROR value in my ini is 0.01

I want to know what minimum value i can set for MIN_FERROR ?
so that my machine gives maximum accuracy
i've observerd that decreasing the MIN_FERROR severely affects
the tuning of beds and causes all time famous and bad "following
errors".

Please put some light over super tuning of machine for acheivement
of maximum possible accuracies. What are the things that limit it
and what things must be done to get an EMC based system running
at maximum possible accuracy

I had posted the same question before on the same forum, hoping that
jon elson, paul, ray henry and les watts may find some time
replying my post!!

warm Regards
@sim