I've just thought of something else with regards to McLaren's development. Remember at the start of the season Vettel was really unhappy with the Red Bull as it was quite nervous and not completely stable. Webber was able to cope with this and was generally faster than Vettel at the first 3 races. At China, Vettel went back to the old exhaust concept, which was clearly smoother and less sensitive to drive compared to the newer solution, however, it was factually proved to be slower. Sure enough come Bahrain, Vettel went back to the new concept, which had a few amendments, and won.
I feel this situation is quite similar to what has happened at McLaren. I think Jenson was struggling to cope with the behavior of the Mclaren, while Hamilton was OK with it. Come Silverstone, Jenson appears OK now and Hamilton maybe not as quick, so they've met in the middle in a way. But the remarks that both of the drivers gave in the race at Silverstone was that the car felt good to drive. So obviously the car feels stable but it has just lost pace. I think this could be exactly the same as the early season Vettel situation where he preferred the feel of the old floor concept, but the new one, although harder to drive, was faster.
What McLaren have done to revert to a more stable car, that is slower, I do not know. But it is a possibility. Maybe they'll sort it in this "crisis meeting".