My question is, if things are so difficult to judge from the lofty heights of the huge 767...
From the lofty heights of the 767 flight deck, if you are protruding out past the line I won't pass, if you are wholly the other side of the line, I will pass. Simple as that really.
Somehow I think this whole "Virgin, please move up to the holding point" has become a bit of a sport lately.
Often it is simply easier to ask ground if we can take C instead (as normally it would involved coordination with TWR controller to get the offending aircraft moved forward) and that is my preferred course of action. It's about reducing time spent with turbines burning, not sport as suggested.
If you can't move up for whatever reason, it's no problem. But without access to your specific FOSOs we will continue to ask if you can move up.
ODL