@Nottsbiker i have just checked out on the acerbis site and seems like the only yamaha tank with a real improvement from mine is a 25 liters for wrf 250/450: http://www.acerbis.it/motorsport/en/product/plastics/fuel-tanks/oversized-fuel-tanks-/yamaha/0008595#a_page
but looking on the net i thing the rubber attachment is different (there is only one longitudinally to the bike instead of two perpendicularly), but i'm not really sure. for the moment i'm waiting for an answer of particular photos of the tank from the ad's owner of the tenere.