Back to that VS 3135, like many Chinese shock springs, these things fall out so easily. They are like KIF springs, so I stupidly tried to use the same method to reinstall, and it broke the spring. Nobody seems to carry the 'domestic' springs, so the choice was to either buy an original Rolex spring, or just get a new balance complete for the same price. So I did the latter
Wouldn't you believe it, another spring came out during installation, even though I had Rodico over it! Will be extra extra careful next time. This time I used a different method to reinstall it, and had no problem getting it back in. I was lucky too - it flew onto the ground, and I found it pretty much right away. It really pays to keep the workshop clean and clutter free as possible.
On top of that, one of the screwed broke (it's as soft as plastic) so I replaced that as well, buying a spare just in case. Good thing I did, because the other similar screw broke as well.
Anyway it runs well now. I'll regulate it tomorrow; it should be a bit better than when it came in.
Here's it is being recorded in slow motion to determine lift angle. You can see the mark I made on the balance to measure how much it rotates. Lift angle confirmed at 52 degrees.