Once the drive plate and new support frame was fully bolted into place a final dial gauge test was done. On the end of the shaft there was 5/1000th of an inch runout. This shaft will be cut back on final assembly to about 11/4" (30mm) when the HRC90 coupling is fitted. This will reduce the runout even more. The coupling is designed to take way more runout than this.
This video explains better than I ever could how the taper lock system works.