When you read the whole saga at Scarbs you can only be amazed that plugging the tunnels improved the car so much. The good thing that they will have a simple benchmark to test any new solutions that they come up with. And it did not come too early.
I wonder what they could have done if the stop gap solution had been found earlier like in Barcelona. Perhaps this what went down:
Seb: The spec A is so much more stable. What has spec B that spec A does not have?
Adrian: Lots of things and the tunnels.
Seb: Can we plug the tunnels to see how it feels?
Adrian: Possible but we believe you will get a lot less downforce
Seb: Lets do it anyway, I need the reliability that spec A without tunnel had
Adrian: I think you are wrong but lets try it.
Just silly imagination but perhaps true.