I haven't tried it, but I'm pretty confident that a standard 17 or even 19 round CZ75 magazine will work in a Rami, though the mag will stick out.. I have one and will give it a try and let you know if it doesn't work.
Edit: Larger standard magazines definitely work in the Rami.
Changing springs as mentioned in the initial post above doesn't seem like a valid approach, but maybe I don't understand...