i have been jumping a G4 M4 for a few years and have no issues packing my Sabre 170 into it. I imagine a 190 ZPX would be about the same. As far as reserve, I have a PD 160 Reserve. You might have issues squeezing a low volume 190 in to a G4. Best consult your rigger before making any purchases. Might be better to get a Optimum 176 Good luck!