Extra300 aileron mass balance

[henry crun]

I have been looking at DamienB's pics of the Old Warden Autumn Show. http://www.pprune.org/forums/showthread.php?s=&threadid=104583

What appears to be the aileron mass balance looks like a sickle shaped mini wing with anhedral tips.
The 5th pic from the top shows this well

Is my supposition correct and if so, why is it like this instead of the usual streamlined blob of lead ?

[Dan Winterland]

They are known as 'spades'. Not only are they a mass balance, they are also an aerodynamic balance which has the effect of decreasing the force required to move the control surface by providing a countering aerodynamic force ahead of the control surface hinge line.

[yakker]

But why the anhedral tips?