Rumour is that the Maccas have to downgrade their diffusor for the next race because the current one exploits the starter hole in an illegal manner. Saying that, the rumour said that we had the same problem, something which the official RF1 denied earlier, so who knows? The diffusor on the McLaren does form around that hole though, something ours doesn't.
Anyway, my point is, they might be chasing the speed they already have rather than gaining any. Fingers crossed anyway.