On my 75B and 75 Shadow, the alignment marks aren't aligned perfectly. It may be due some of the pistol upgrades, but the Shadow was not aligned by the marks when new.
With the left hand, align the marks and push with right thumb while retracting the slide just a little more past the marks . I push against my chest for the added movement.
![Shocked :o](https://czfirearms.us/Smileys/default/shocked.gif)
Mine will then push in with my thumb enough to be able to pull it out with the other hand. I do have to push hard but no blood.
It's okay not to believe me.
![Smiley :)](https://czfirearms.us/Smileys/default/smiley.gif)
I also did it for a range friend with an SP01 to tighten his trigger bar spring screw.