Porsche built the Flat 16 in response to rumors of Ferrari building something similar and they actually put in a car... the 917 with it was a longer car (for obvious reasons) and this really upset the handling. In "The Unfair Advatage" by Mark Donahue, Mark talks about the project and goes into what they did and more including the 917/30 which they took to Taladago circuit with 1500bhp in 1975 to set a new world record of 221mph of an AVERAGE lap time. The cars top speed was over 260mph and this recrod stood until 1990 when the Indy cars finally caught up.
Love this stuff
Oh... one book which if want a good read....
The Unfair Advantage, Mark Donahue. It's back out in paper back and really worth reading. I couldn't put it down!
Mike Ghia