It's certainly something I've wondered but never asked Acid about.
If they start at 600, you've got to be talking 800 > 900 I would have thought.
The only thing I can see that might be a problem is putting the power down, I read somewhere that guys in the USA have tuned them to silly power levels with no reliability problems. Mine has a Quaife LSD and it is so easy to loose traction with 600+ so God knows what it's like with greater power. Plus the turbine smooth way the car just gathers speed is something I wouldn't want to alter.
I've just found out that there are only half a dozen technicians who assemble the V12 Uwe Grober who assembled mine also assembled engines for the SLR's.