Can anyone explain to me PLEEEEASE. Why this is happening to my hoodie mesh in CC4? IT starts in a generic A-pose. I get it to fit to the character properly (Transfer to clothing, Conform, skin wieghts) But when I move the character into a T-pose it stretches like mr. fatastic under the arms. And when animating small spikes like the ones in the PIT level of morta kombat shoot out in a couple spots as if the mesh has lost it's mind. Been working on this for a week and cant figure it out.
THINGS I HAVE TRIED TO FIX:
1. smoothing the mesh out in EDIT MESH. RESULT: when the arms are lowered it PUNCHES A HUGE hole in the characters side.
2.PUSHING vertices and faces in while in T-pose. RESULT: PUNCHES a hole in the characters side and comes out the other side when arms are lowered. Please for the love of god if anyone can help I'd love it.

Editing cloth mesh is not going to help and would make things worse as you have learned.
Such type of cloth should really be fitted and weighted in T-pose to begin with.
Where did you import a hoodie from?
You can simulate it over in Blender (if you do not have Marvelous Designer) from A to a T-pose, import back to CC and transfer weight in T-pose.

Or you may convert it to accessory in T-pose (baking a shape), use sculpt brush to distribute the mesh properly under arms and then Transfer Skin Weight.
Note: It is not possible to simulate 100% correct behavior of baggy cloth items with just bones weight influence.

Here, I did mess up this hoodie and then fixed it with second method I mentioned. Your case seems worse and you'd probably have to spend more time.