I tried one out of curiosity on my G32 (same size as a G19) and it worked just fine. It supported the pinky instead of the ring finger like on a baby Glock. There is a 1/8" gap in the front of the bottom of the mag due to engineering differences. It's just not needed since I get a full grip as is. If you have one, try it!
Luck will run out, but skill will survive.