Geez, this is going to hell in a hurry. There's no right or wrong setup for the SC10 or any other car. Driver preference, track size and conditions, etc. all make a difference. It's like asking whether it's best to run a spool, diff, or one way in a TC. But, the pinned shaft is an easy mod, and it's cheap. If you don't like it, pull the pin and it's decoupled. Takes what, 30 minutes, and gives you another tuning option, why not? And it sounds like what I said 6 pages or so ago is probably correct. If you pin the top shaft, you need to run either the stock slipper, or loosen the slipper with the Garodiscs or clutch basket. A properly adjusted slipper is the best insurance for your drivetrain.