I think it depends on the individual, and how long you've been injecting. I'm not huge (6' @ 185, <6%bf), and I put 2cc in rear delt with no problem at all, and I've done 2.5cc with very little pain, and only for a few hours. Glutes no problem; after all, a dr. will shoot 6 or 7 cc in a glute, if necessary. If I load too much in one muscle, it will hurt, and I'll back down next time. I'd rather put it all in one spot, than stick twice, and waste 2 needles. I do remember that my delts would only tolerate 1cc at first, but I worked up. The only place I've had trouble is quads. I got a bad deep muscle hematoma last spring, which took 2 months to go away. My whole thigh was swollen huge, and I couldn't squat, and it HURT like F*CK for weeks. I think I hit a deep artery or something, and maybe I went a little too low (closer to the knee than you're supposed to stick). And I have skinny thighs/legs, which I think made it worse.
As usual, the disclaimer for anything I write here, is that I'm not a doctor, and don't take anything I say as advice or suggestions. I am only sharing personal experience with regard to how it affects me.
Charles