I used to fuel jets back in the day, my rule of thumb was to be somewhere between the dispatched fuel load and 400 lbs. over; sometimes I'd ask the crew if they wanted more, when they did, I'd simply give em' what they wanted, or close to it. Most guys were cool with it, even had a couple say the only time too much gas is a problem is when the plane's on fire
The way I see it, I was there to do my part to make the flight as safe as possible, if they wanted more, they got it . . .