A light padded Gambeson. A battle with iron weapons I would therefore not risk, but for LARP weapons he sure is serving. The leather straps for the lacing are a bit short. As undergarments for my chainmail of Gamebson is ideal. It is relatively narrow and cut grade, so nothing rumschlabbert, the leg line is (short and thick Bin - Size M fits very neatly because) ideal for me. The arms are wide enough so that you can still set a bit on the upper arm: D
You sweat like hell in it even if it runs through under the arms. But that is sure about it also from the unaccustomed exertion with the chain mail.