Exploring this possibility gave us very interesting designs in 1983 (from when I figure that Tyrrell is) and 1984, before a rules change made the wings return to more conventional forms. This came after the ban on full underbody ground effects, when the F1 engineers faced a substantial reduction in downforce and started looking seriously at wings to compensate.
In the end, spectacular at it may be, that Tyrrell design was a flop. This was the solution most teams adopted:
The "winglets" outside the main wing provided the extra downforce.
Being a Rory Byrne fan, this Toleman solution was my favourite:
The most forward wing is effectively detached from the main one and is placed in a higher position not to mask the main one. However, this limited the incidence possible in the additional wing and Toleman eventually reverted to the more conventional solution.
On a not entirely related note, is there much difference between mounting your rear wing on the endplates (BMW,Honda) v pylons (Renault, McLaren, Ferrari etc.)?? Do the pylons have any aero effect? Or does the wing-mounting decision have more to do with the concept of the car as a whole? Thanks in advance, and if it's been discussed in another thread a link would be appreciated! 
