Went shooting yesterday with my G19 Gen2 and a G17 Gen3 in which I sanded smooth the finger grooves with 600 grit Emory cloth (I took a file to it first to take out the lumps). I was careful to remove only the finger grooves and if you look at it sideways, the surface where the finger grooves were is slightly above the surface of the Tetris-block checkering, so I am fairly sure I didn't remove frame material.
That said, shooting the G17 felt slimmer in my hand than the G19. Is the Gen2 grip thicker front-to-back than the Gen3?
All that aside, I will say I'm really looking forward to the 17M/19M!