19l tank and have had well over 200 miles out of a tankfull several times.
personal best so far was 214 before filling up.
last 20-30 mile is worrying like... only ever run it dry once though and that was cos i forgot to connect the level sensor up & the light was on all the time.
just work out what it does to the litre and see how much you are putting in from the lamp.
ive usually got 5-6L left when the light comes on, which is easy 50+ miles.
depends how it's ridden.
keeping under a ton it gets 150+ to a tankfull easy.
certain members here do not believe it can be so economical, but that's cos they'd have to screw the nackers of theirs to keep up with mine
(but saying that, it's not so frugal with the 50 pilots in lol.... on 45's with mixture set weak it was brill on petrol but not the smoothest of rides below 3k)
re the bigger tank - you'd have to fit something wider i reckon, but to do that you'd need to be using different bars, like renthal sport bars, otherwise the bars would touch the tank - mot failure ;)