Have you tried a "pinky ledge" magazine base plate on a G29 magazine? I tried a + base plate but didn't like it whereas the pinky ledge did the trick for me.
Bbl length is 3.78" for the G29 vs 4.02" for the G19, as I'm sure you know.
YMMV,
Keith
ETA: A threaded barrel would regain that .24"...