Need help with welding arms to torso in the correct position

I’m working on a dress-up system with custom body parts similar to Royale High. The legs/heels are working fine, but I’m having trouble with the placement of the sleeves/arms. Originally, when I added them to the system, they ended up attaching to the lower torso instead of the upper torso. I then tried adding a root part to the arms, which did attach them to the upper torso, but they’re positioned too low. I’ve attempted various adjustments, like moving the root part and adjusting the arms’ height relative to it, but nothing seems to fix the issue. Any help would be really appreciated!