The free travel of the suspension is related to lowering blocks. You shorten the spring travel by the thickness of the lowering block. My springs sagged a little. Instead of buying new springs, I had the lowering blocks removed. Now, for 5 years, the spring travel has remained constant and there is much more suspension travel. The other advantage is that the axle is now directly on the spring. This gives much more control when cornering. In my experience, it's better than a Panhard rod plus lowering blocks. When I removed the lowering blocks, I had to remove one of the two layers of rubber bump stops on the upper side of the axle so that the axle could swing out properly after compression.
I would agree with everything Montgue says about the ATBs. You did an excellent write up!
Here is the original report with a few pictures on more of the following pages.
https://www.talkmorgan.com/ubbthreads.php/topics/670243/re-rear-springs#Post670243
