[QUOTE]Once the slide is on, I have to line up the notch marks so I can place the slide stop in the correct position to slip it in. However, as I hold the slide in place (under pressure from the spring)[/QUOTE]
What spring pressure? Unless there is something majorly different with STI 1911 guns, there is no pressure on the slide.
I have several 1911s and it is true the slide stop does not always want to go in the way it should.
Once I have the rod inserted into the link, I move the slide back to the takedown notch and set the end that pushes the spring right on top of the end of the retainer pin.
I make sure it has some grease on the end as that makes it a little easier.
Usually a light tap with a plastic screw driver is all it takes. Pushing the lever up will get you that idiot scratch we all hate to see.
The last thing I do is tension the recoil spring.
Maybe I am reading your post wrong