Elderly has ordered a (some?) Martin 000-28 Herringbone models... I've not played one, but am intrigued by them. Maybe a call to Elderly can get you the specs as far as bracing and string-guage recommendations. Also, don't believe the price on these, as it's probably listed IAW Martin's MAP policy. A phone call will get you the real price.
http://www.elderly.com/new_instruments/items/00028H.htm
Have you joined the Martin forum? I'm sure there are folks over there that have played the Mayer as well as this Custom 000-28H.