Back in my previous life flying RAAF B707s we used standard weights which was fine until we carried a plane full of fighting fit soldiers and all their kit out of Honolulu bound for Richmond. We were at MAUW on departure and the poor old thing only just got airborne and then staggered into the sky and took ages to accelerate and would not reach the planned cruise level. We did some head scratching after we eventually settled in the cruise and worked backwards through the performance chart to discover were somewhere like 8,000 lbs over max weight on take off.
We used to weigh them after that and couldn't generally plan PHNL - YSRI non-stop with a full load of soldiers.
Using standard weights in airline operations I'd wouldn't be surprised if the actual wieght of the aircraft varied from the planned weight by by a minimum of several tonnes, up or down, most of the time. I'm not sure whether the 'standard' pax weights vary depending on the departure point, some races are generally of smaller stature than some others, I'll have to check next time I'm at work.
Regards,
BH.