MD Tooling makes what you are asking about for the 2000SY. You wouldn't necessarily have to use a spring loaded holder. You can use the machine's
G300 torque control to handle the positioning and the applying of the proper load from the B axis to hold your long parts. Here is the link for MD Tooling's sub spindle removable tail stock attachment.
You can read about the torque control in your Doosan Operator's Manual.