ok simplified.
WITHOUT RAIL CALIBRATION:
There are 100s of GC1s and GC2s in the world that are fitted with K66----plays slower and banks long compared to original cushions
There are 100s of GC1s and GC2s fitted with K55--- plays like a pinball machine, play area is smaller, and banks shorter than the original cushions
WITH RAIL CALIBRATION:
GC1s and GC2s play absolute best with subrail calibration and K55s.
Oh and 3.5 to 4 rails isn't terrible.
Notes:
All rubber is not created equal.
We have all three types of goldcrowns in the room where I play.
We have 6 tables set up with K66 Artemis
We have 2 tables set up with K55 cushions
and we have 11 tables with the original cushions.
Do a search on Subrail Calibrations and you will find all the information you need and then make a decision on what you want out of the table.