Metkap and I verified the feasibility of using this tool.
1st The progressive spring tool did not work on an 07 shock. The Clinic provided the bail out.
We bought two flat Flanges for $10 1/4 in thick. And had the other things on hand.
But not having done this before and unclear instructions posted we had to do some guessing.
Although it was posted the clip is at the 'Dead" end. My spring did not show it with out some coaxing.
Following picture shows Poor mans spring tool and the needed coaxing. We really compressed this spring and seen no clip, but when I tapped the eye and of the shock it quickly revealed the clip. So not that much compression is needed.

Following pic clearly shows the clip you are looking for.

You don't have to remove it from the shock. Just from the grove and slide it back, Clean the grove it goes into while your at it, you want it to fully seat into the grove again, no rust or trash.

Here is what it looks like all apart. Be advised you can put it together wrong (retainer ring on wrong side Ha ha I got more practice with this tool than anyone.

So pay attention how it comes apart. It's is a little dangerous. I'll note that we used on hand 3/8 in all thread and wished we had used 1/2 in when one of the nuts stripped on the thread. Luckily we had a bail out on the other end to loosen the tool and get it off so. if your thinking of using bolts this long, don't.
Hope these picture make it more clear than it was for me.
Progressive spring is worth the money though and ordered direct from Paccific coast and got it in 5 days.
Now the front seems stiff compared to the rear so how about ordering the progressive front at the same time.
Ha ha.