I just finished the test drive after following the steps here. Ride quality severely improved!! Pushing a thin popsicle stick into the old ones would go alllll the way in, very bad.
Discovered some other issues with my SLS. First, when I went to bleed the lines, nothing happened at all, no fluid and no movement or noise. At first I was reconsidering what was really wrong back there. But I decided to push forward and was glad I did. The fluid was very contaminated, looked like 50/50 motor oil and hydro fluid. Now, I'm off to order the SLS valve rebuild kit.
I think the pump is doing ok, for now. I cracked the return line and there was pulsing fluid flowing out. But, the fluid I see in the reservoir was a lot cleaner than what came out of the lines in the back. I'll have to revisit that SLS familiarization thread here to confirm, but maybe it's just creating two closed loops and the fluid stuck in the back slowly is diluted by motor oil.
Earlier this year the feed line from the pump was replaced and the system drained and a new filter installed.
Edit: I lost about a liter and had some on hand to replenish but the level stick show I was still good, both before and after the car was running. Maybe another sign of how a bad or leaking valve will isolate the lines in the back. I will try and adjust the ride height to see what happens.