Talking of bigger tanks, I have one of those german-made plastic ones. It came with about 19L capacity (OEM is 15), but it said that once fitted and filled up, it would expand a bit to a capacity of 20.5L
Well, it did expand. So much so I can't take my side covers off anymore! And, as I put in new brake pads and flushed/bled the system yesterday, I found out it's also become rather difficult to remove the rear brake fluid reservoir cover as well!
More fuel, yes, Slightly better range, yes. A helluva lot more hassle, yes too!