>>76496508
Hmm shouldn't hurt if it's impingement since the whole rotator cuff should have already passed under the arch when your arms are high. Could also be acromio-clavicular arthritis or issues (causes pain when your arm is basically vertical).
I don't think your arm should feel like it's going to slip out of the socket though. If it's too intense you can use your feet so you're not supporting your whole weight and build up to full weight dead hangs. There's some doctor that wrote a book (pamphlet really) about deadhangs for rotator cuff problems you could go pirate but it's not really worth it since it's literally tl;dr do deadhangs lol with some cat scans showing the joint and a bunch of testimonials.
Granted I'm no expert just a random guy who has had similar problems.