5.8 gals would definitely give it the range I wish it had. But as others said, it's not particularly attractive, and puts that extra 6 or 7 lbs up awfully high. Pity they couldn't expand the sides of the tank under the plastic side panels. The weight would be lower and you wouldn't see the cosmetic change.
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.