Having walked that same path during my T5 install on a 56 235 (6 volt flywheel) I found that even though you have clearance at the outer edge of the disc it is flexing and binding up in the center....that's where your drag is coming from. I've documented the process that I used in extending the splines and verifying that the disc will actually slide far enough back to completely release in my webshots Shoebox album. (page 5 or 6) I used the rcf-4201 disc and haven't had any release issues since I made the modifications and have switched it to a 60-235 with a 12 volt flywheel. Hope this helps.
Dave
