Tailoring chainmail sleeves can massively improve the armours overall weight, mobility and speed. Ideally, the mail should fit tightly around the arms and have no room to swing. At the same time, the joints need to be lager to allow full bending. Therefore a triangle shaped pocket can be inserted at the elbow.
For tapering the arm a stripe of mail can be inserted to create two smooth looking seams instead of one. In either way it’s best to place the seam at the bottom or lower backside of the armpit. Alternatively expansion rings can be distributed evenly around the sleeve.