Hi Simon, Ah, that explains it, great to know we've got an ex CTI'r amongst us. I've got the NACA Duct and also access to a 485 bonnet. This has confirmed that there is symmetry across the two sides, but only if installed at the same distance from the bulkhead. However, the dept of the NACA Duct in that position on the RHS won't work - as the pedal box means there is not enough space for the NACA Duct. So as far as I see it, I have two options; 1) Risk trying to fit the NACA Duct further away from the bulkhead - albeit the curve of the bonnet reduces along its length, hence may not be a good fit. 2) Seek to reduce the size of the pedal box - ideally flat as per the LHD Caterhams (eg 485). Hence, any input on this also appreciated, eg why is the pedal box "flat" on LHD, yet "boxed" on RHD. With thanks Chris