Since much of my learning curve for porting evolved around messing with 906/915 heads, and “what worked for me” on those heads included a fair amount of SSR reshaping, so when I had flow regression issues at higher lifts on other heads, one of the first things I would do is some tweaking of the SSR……..and more often than not, it would show improvement.
Often not 100%, but it was usually “better”.
I’ve spoken to other porters who don’t mess with the SSR until the last thing.
But I usually start rubbing on it earlier in the process than that.