Lyka,
Thanks for the detail; I'm happy to accept that I may have been misinformed (although my source was pretty good), but there is a dearth of (detailed) information on the subject. However, a lot of people still need a lot of convincing. I don't mind doing Config 3 landings, and quite like doing them for the team (200+ landings a year * "20kg" is a lot of fuel); in fact, I'm nerdy enough to log whether it's Config 3 or Full in my logbook. I still feel that there isn't enough focus on saving fuel in the rest of the sector; it's almost as if the emphasis is wholly on the landing Config, whereas a larger saving is to be made elsewhere. For example, I'm quite pro-active in trying to get shortcuts, but some guys will just stick with the flightplan.
Very interesting about the 321. I don't fly it, but a lot of guys who used to fly it would swear blind that it's a bad idea. Again, education is key.