I tried modelling a lot of sleeved tops for Apollo using Shade and Hexagon - I've noticed that it's not just his extra joint in his upper arms, but also that his arms are flexed in zero default pose throughout the XYZ 3D space.  This also makes it tougher to adjust converted clothings from figures which have zero default position of the arms in the XY plane.  But then again, I ain't no professional clothing modeller, so....

Eternal Hobbyist