Well fluid dynamic drag isn't my strong point but I think he's basically saying a 109G6 could theoretically be cleaned up aerodynamically for a top speed of 800kph? Not sure you'd be able to do much once you got there except hang on in abject terror but it's an interesting proposition.
Plus it's the bulges and blisters that give the G6 all it's charm, would be a shame to lose them just for another 200kph.
Nice link, thankyou.