I see that I wasn't paying attention. Per 10-53 in the service manual, all drive plates are 2.8 ± .08 mm thick. That means that the stack height is 10*2.8 + 9*2.3 = 48.7 mm (1.917 in) when a 2.3 mm ninth driven plate is used. The ±.3 mm ninth driven plate option may be to allow that height to be achieved when the drive plate variations stack up. At least that's the best that I can come up with right now.
I can add that to the K5/K6 service manual if a fairly broad consensus can be reached here. However note that this is for a new clutch. Used drive plates can be much thinner and I don't know what to do about stack height there.
Finally, in partial answer to DutchGSX-R1000's question from five months ago, the OEM spring free length is 57.01 mm and they should be replaced at 54.2 mm. His winding counts seem reasonable when compared to spring pics but I can't be more specific than that. No idea of wire diameter. Coil diameter is also important but it can't vary much, given the constraints of the head.
I can add that to the K5/K6 service manual if a fairly broad consensus can be reached here. However note that this is for a new clutch. Used drive plates can be much thinner and I don't know what to do about stack height there.
Finally, in partial answer to DutchGSX-R1000's question from five months ago, the OEM spring free length is 57.01 mm and they should be replaced at 54.2 mm. His winding counts seem reasonable when compared to spring pics but I can't be more specific than that. No idea of wire diameter. Coil diameter is also important but it can't vary much, given the constraints of the head.