Alright the easiest way to get started is to take your rami and remove the slide stop, now looking in the slide stop hole closest to the safety pull the slide all the way to the rear. Watch the groove in the slide that the slide stop pops up into and it's relationship to this hole. Now swap slides and do the same thing and you will see that the compact upper slide stop groove needs to be lengthened to get the slide stop to work.
Here is a pic of the stop where material needs removed.
What is the XCR I have heard mentioned a few times?
Go to the link above and on page 3 you'll fine the XCR and a rami with a compact slide.