bad sholder deformation

I’v put a rig on a simple girl model one time and it deformed fine. I do not see why I have been having troubles with this one. For years I have not gotten the shoulders right. I will add shape keys to correct the deforming but I want the mesh and the bone placement to be inspected. I have adjusted these and still can not get it right.
As I write, I see, I want to pull down the lat and make it lower near the body. I think that will help much. Oh I think it is modeled poorly! I still want to post and ask about the Shoulder mesh and bone placement. The arm pit is too high.
What is wrong with the Shoulders??

Yeah you’re suffering from something I like to call Noodle Shoulder Syndrome. It’s all down to the topology. Your shoulders have the sort of topology that is better suited for elbows and wrists, so it deforms more like that than a shoulder. Shoulders will deform best if you have face loops that go from the chest up and over the triceps, rather than running straight down the arm. The shoulders flow across the chest and out over the top of the arm, then the arm is extruded downward from there. The topology you have is a symptom of modeling in T-pose; it’s natural and tempting for a modeler to want to extrude the arm straight out of the hole in the shoulder in that pose rather than the way it should be. Basically when you’re modeling shoulders you have to think about how the shoulder will be shaped when the arm isn’t in that basic t-pose, and create topology for that instead of the pose you’re in. Here’s a simple example. HumanTopoBase.blend (521 KB)

Ok. Im going to redo the solders. I like T pose to me it seems to be 1/2 way from up and down. I know arms are down more then up. I have looked at many many meshes but one more is good. It will not take me long to redo it for a test. I have seen the loops like I have work well but it is not working well here. I need time to study the mesh. I just want to do the shoulder the best I can and live with it. This mesh has been redone before, I do not want to redo again.
back to work on this . ill post the new mesh.
Thanks for the help

That example model notwithstanding, I usually model in something lower than a t-pose. I usually have the arms only raised maybe 50 or 60 degrees from the torso, with the elbows slightly bent. With some variation on that shoulder topology the deformation usually looks fine without any weight tweaking or helper bones. Those edge loops that go from the top of the shoulder down onto the triceps should just accordion together rather than bending. Sometimes the exact placement of the shoulder joint makes a difference. The pivot point in a real shoulder is a bit higher and further out than I think it appears at first impressions.

@KHorseman, Hey! that is a nice base mesh. Would you consider releasing it as Creative Commons?