After a couple of hours at Sanspeed today, we found that the BMC Carbon Airbox can't be fitted, there's just no room.
I had a good look at the standard airbox, you basically have a very good cold air feed but then you get to a thick gauze layer then a paper filter, all very restrictive. I'm going to relace this with either a BMC or K&N replacement cylinder filter. This should happen next week, I will post results.

Gavin