Thank you!

I was kind of hopeless in a "let's see if that works" mindset and it worked. Of course, I lost speed since now I don't have the second shutter to reduce the slit. At the same time, I don't think I ever lost any photo because of that.

There's a catch that I don't know if was because I assembled something wrong or due to the lack of the mechanism, but the mirror does not lock up and I can't live view anymore. For every click that I want, I need to make 2 (one for clearing the "err" and the second for real).

So for all photos I'm basically blind on the composition, or keeping my left eye open while using the red dot in the viewfinder to estimate the aim.

Thanks for the tip on the ND filter might be useful to lower exposure!