I didn't see any real improvements in efficiency between the Lectron, Smart Carb, and a well tuned Keihin. All working on a fresh engine with tight squish clearance.
I carry an extra litre in my backpack which gives a total of close to 11L (pretty sure I can squish a bit more than the 9.5L into the tank). Regularly ride 115-120kms of mixed terrain on a tank over around 3 hours.
Given most other riders are on fuel injected 4T's (and some with large tanks as well) and get better mileage than us, it makes sense to simply carry a length of fuel hose which you can use to syphon some into your own 1L bottle.
Always carry enough premix to make another 10L of fuel so I can either mix a litre on the side of the trail scabbed from someone else, or if we want to more kms we factor in a fuel stop somewhere. In a couple of cases we have had fuel stashed in strategic locations, but this takes foresight and planning.
Most of my riding is in the sticks with a few transport sections. I'm generally on the throttle in the tight stuff, and back off and putter in the open sections. If I rode more open terrain I'd gear it taller and probably see even better range.