I just reversed mine, but unfortunately won't be able to test tonight due to prior engagements. I did notice however that the mag catch in mine is metal. The paint finish is still on the nub that fits in the slot on the mag, so I am starting to think there may be something else going on. Perhaps there is too much play in the hollow of the grip? I can feel a bit of jiggle from side to side, but can't pull the mag out by hand (I'm not ripping on it or anything - but I am applying a fair amount of pull).
I was very careful removing the right side plate as per the advice given to me, and the spring stayed in place.
It looks like it would be a bitch trying to find that thing, had it decided to pop out!