For me, another 1/2gal wouldn't be bad. Any more than that, it's extra capacity I won't ever use. Couple of times I went more than 150 miles before stopping I did only to test out the fuel tank's range. Probably rode past at least 4 gas stations in the last 30mins each time. Had to over-rule my protesting right wrist while I was at it.
This is a very sporty sport tourer... not a grand touring mile eater. It sure as heck not a GS meant to conquer Kilimanjaro.
8 gal tank on the VFR1200 would be like beautiful huge breasts on a prima ballerina. Lovely to have... but gets in the way for what she does best.