Binder: Underworks^® Tri-Top Binder, Medium size
Chest size: 34"/86 cm
Issue: Digging into the area near my left armpit

I just got my binder a few days ago, and it has excellent compression, especially taking into consideration the fact that my chest is rather large. The only problem I have with it is that on the left side of my chest near my armpit, it's been digging into me a bit. Not on the right side, just on the left. I'm wondering if this is an issue with the binder or it's just too tight around that area. Does anybody else have this problem with their Tri-Top Underworks binders?

I had a similar problem and wearing an undershirt under it usually helped prevent it.

I've been hearing some talk about that being helpful.

I've never heard of that happening on just the one side before.  Are you larger on that side than the other?  If you are perhaps playing around with how you arrange things on that side might help, I find that sometimes different things work better for me on different sides.  I think one of mine is a little denser than the other.