I went down a similar route with a new EMC shock from fleabay which was specifically for a TriArm. As it was new it performed excellently, used an original Honda spring for the TriArm, NOS again as the spring with it was far too strong. Set up your static sag and you'll be well pleased.

BTW when modifying a rear linkage to increase ride height, what is the ratio, I worked it out to be 1:1.74, so how does this relate to moving the hole? ie to raise the rear by 5mm, move the hole 8.7mm or vice versa, and which direction, nearer to the bush, or further away? (I've filled the holes with weld already, I'm just ready to mark out the new position of the holes.....)

And most importantly, what is the recommended increase in ride height?

Would this fit an nc29?

Wont fit the NC29 Im afraid.

As I started this topic, I though I would report back after some track time with the set up.

I had this shock and a 17inch nsr250 at the back, and against a track day I did with the original shock and 18 inch wheel, all I can say is it was the best money I have spent on any of my bikes over the years.

Was so much more responsive, quicker on turn in and stiffer I also had much more tyre choice! The rear wasnt wallowing around, not to mention a decent amount of set-up options compared to the standard shock. I dropped the front forks around 20mm, raised the rearsets up and had a much more productive and enjoyable day.

I dont have the 23 anymore, it was sold to a friend and Im back to the 600's but it was a blast and I would recommend the modifications I made. I can safely say that the 400's limits in terms of entry speed and braking points were greatly improved by the work done. It is also a pi55 easy job to change out the shock!