I pinned ed for 6 weeks before and it was just fine without delts in the rotation. With the quad, i like to shoot center or just right of center and around halfway down. You can shoot the quad in completely different locations, it's so big.
I gotta remember to say with quads, there's a lot of veins, for me anyway, try to avoid them. I've hit nerves a bunch but it just feels kinda funny for a second, not so bad.