Bumping this back with kudos to the OP for starting this great thread.
I've got a couple of Avocet O2's I want to recover and need advice on what thickness leather to order. As near as I can tell the cover thickness as removed is about 1.0mm. What I don't know is how much the leather stretched to reach this level. 1.0mm translates to 2-3 oz leather but this is thinner than what was mentioned earlier in this thread (5-6 oz). Any suggestions that don't involve buying an old coat? I'm thinking of ordering from ebay.