Formula 1 is not purely aero,and even the best teams forget this now and then.
I do not say it is impossible to get a twinkeel car right ,but it is a big task and you surely have big challenges to master in addition to whata single keelcar needs to be competitive.
A big problem arises if you cannot setup the car mechanically where it needs to be aerowise,and this is what happened and still happens to Williams.their Problem is compoundet by the stiffness /vibration Problems their frontwingsetup has.I´m sure there is a operating window but it is a bit smalland knife edge.
Let´s face it Williams has lost the plot,as well as Mclaren was off the map for awhile.the strength in depth is big enough to find back ,see Mac,but just look at Mr Neways face and you know these guys have worked their heart out to find back to speed.
On the other hand the aerodevelopment onWilliams side is creaping since winter indicating that all their ideas to improve did not produce the needed results....and..they produced illegal parts on top of that wich indicates they are quite desperate if they don´t even realise they are outside their allowed envelope..