...fuel cap leaking if I brim tank on centre stand then park on side stand,
Yeah, it has the leakiest gas cap I think I've ever seen. I've taken to keeping a cloth in my pocket to wipe down the tank. Even with underfilling, sudden acceleration or braking can cause a leak.
Averaged 87 mpg so far too...
I recently did an 800 km trip (400km one-way). My speed on the first leg was in the 100 to 110 km/h range and consumed about 15 litres, which works out to about 75 mpg Imperial. The trip home was at night, in the rain, and I kept my speed in the 70 to 80 km/h area on secondary routes. I only used 11.4 litres.
That's almost 100 mpg Imperial. After 400 km (250 miles or so) I hadn't even hit reserve. Most folks don't want to drive at 50 mph though. :-)
Keep it tight, keep it lubed, make sure that seal on the airbox is good and tight, and - while you've still got the enamel on - address that issue of the speedometer cable rubbing on the front mudguard. It wears through quickly.
And have fun!