Agree completely with Has2be, it is not an upgrade, but a repair. I own a RM6SB and made the repair and it completely transformed the sound from the turntable. However, this has been a disappointment in two areas. The first is about the industry. There are a slew of audio reviewers that have given these poorly-designed motor-suspended turntables great reviews, and these accolades came from authorities who have hi-end "associated equipment." I have a medium end associated equipment system and was able to detect the problem almost immediately.
The second is that I the consumer had to discover and fix the problem on my own. I was fortunate to come into this toward the end, but there are many who spent time and money on replacing motors, spindles, and belts that were never broken.
Regarding Henley Designs, they are a distributor of Pro-ject and their parts, not Pro-ject. Henley worked with audiophile Alan from AppleChap to develop the fix. Alan is the real hero in this story. As far as I know, Pro-ject the company has not taken responsibility for the problem.
So the moral of this story is you will have to spend money to fix your Pro-ject turntable, but the real moral is that whenever you mention your Pro-ject turntable you will need to refer to it as a "motor-suspension fixed" Pro-ject.....