So many threads get started asking about fit opinions and or solving aches and pains. Well, today I have confirmed that my fit is perfect. Previous pains have totally disappeared after endless tweaks and experimenting.

80 miles and no more lower back pain, nor shoulder ache, nor hand numbness. Comfortable throughout the ride and after. I didn't even get a pro fit!

how did you achieve this fit?

This thread is not very useful without you telling us

ok then. if you insist.

I started off adjusting the saddle height until it felt comfortable and allowed me to extend my leg but still keep a bit of bend at the bottom. Then I fiddled with the fore/aft until it felt right. All that Kops stuff was a starting point but I didn't like it there. I felt I couldn't pull back properly and so the pedal stroke was uneven and hard to do circles. Pushed it back by mm and until it felt better. all these changes were small and I did a whole ride with the new change and I changed one thing at a time so height or fore/aft but not both. Then when the saddle was ok, I dealt with the shoulder pain. I felt too much weight on my arms hurting my shoulder and numbing my hands so I got a longer stem.

I'm on the same path as you. I have lowered my saddle until I have a decent knee bend with a flat foot. That alone has saved my ass and solved a lot of uncomfortable saddle issues.
Then, working on the fore/aft. I have also started around knee cap/end of crank. Too much weight on hands though so I moved it back, under about 1cm. I feel balanced but my bars feel a bit too far out. Causing some elbow pain. If I go too far back I get perineum/soft tissue issues. Handling is also affected by this. Too far back and front end is not planted on turns.
Bar drop has also changed a lot. I am currently with a 1cm drop. Once I get a FSA Wing Pro Compact, that will change a bit I think.
Also, I am considering getting the Speedplay extension plate so that I can put the ball of my foot about 8mm forward of pedal spindle. This will allow me to lower saddle and lessen the bar weight without pulling the saddle back too far.
Lastly, I have learned that sitting properly on the saddle makes a huge difference. Sit on your sit bones, don't turtle neck and bend at the hips not the lower back. Ride with a rounded back and shoulders, slight bend in elbows. Steve Hogg's articles have been very helpful. Pelvic stability on the saddle is paramount.
Incidentally, my two "pro" (static) fits from Serotta fitters have left me less than satisfied and learning what makes me feel better has been more helpful. Being willing to try different stems, saddle heights, fore/aft have been a learning experience.
Hopefully, I will have my "perfect" fit figured out very soon. I can say that I have not experienced any back pain, neck/shoulder pain or knee pain.