Another garment that might be worn under a brig would be a pourpoint. Which is a sort of vest like garment. It would seem to follow the shape of the brigs I have seen and it is laced to the hose so it would not rid up. This might also help hold the shirt in place as well. An archer might not wear a heavy padded coat under his Brig. So his arms could move freely. A lot of illustrations form the time show at least short mail sleeves and mail around the waist. We can not be sure if this was a full mail coat or just sleeves and I hope I am using the right term a mail skirt.