I am part of a medieval reenactment group, covering the time between the 11th and 15th centuries. While it is acceptable for us to buy our costume/armour, etc, more kudos is awarded for self-made items.
I'm thinking of making myself a gambeson from leather (with padded lining, of course), and my questions are thus:
1) Would leather have been used for gambesons in those times?
2) Would it be period-complient to wear it over maille, rather than under it (this being a the backup plan if my maille hauberk doesn't fit over it)?