Inner biceps and upper armpit were the least painful for me. The worst area has been the inner elbows, especially the inside over the bony part. The artists at the studio I went to told me they get a lot of people coming in for sleeves who leave the inner elbow until the end, or sometimes skip it, and the two artists there who had half sleeves both stopped just above there. I am SO SO SO glad that I will never have to go through that pain again. My left arm was the worst - I almost fainted, I silently cried, I couldn’t speak, I was shaking... Nothing else has come close. All of the artists were warning me before we started, but I didn’t think anything would hurt more than ribs and lower armpit. I was very wrong. Prepare yourself. It was worth it but OMFG.