Generally speaking, I think if you want 23L, buy a Tenere. I don�t like the way a Tenere fixes the lights to the tank. I don�t like it on Transalps, I didn�t like it on Dominators, Ducati Multistradas, Triumph tigeror anything else. I know it isn�t justified but I like the light to point where I am steering NOT lagging fractionally behind.

Back to tanks, a big bulbous 30-35L jobby on the XT660R (where the wings are extended down lower and forward slightly) is starting make the bike, really different and a big distance touring entity (650km+). The Safari/Suzuki DR650 30L for example, (this bike was 2nd choice), looks good but you could easily (stylistically speaking) pump out the bottom wings and gain 2.5L per side. Of course the problem then would be getting fuel up to the fuel pump and gauge etc on the XT.
Solution 1: fuel pump doesn�t have to be in the tank does it? I can�t see that a small housing couldn�t hold the pump below and behind the cylinder (there appears to be some unused space around the air intake). This spot allows gravity feed and the gauge indicator to work.
Solution 2: have a small housing inside the tank that holds the pump. Two small feeder pumps, (one at the bottom of each wing), that pump up to the factory standard pump in its mini housing.

I like the concept of a touring range of 700km. The only bike even close to looking at that range is a:
BMw - f800GS with a toura-ugetyourgearwhenwegetaroundtoit-tech oversized tank. *still annoyed about the chain guard TT.

Or

Something like a hdt/Kawasaki modified diesel army scout bike.

Does anyone know how hard it is to make plastic blow moulds???