As Tony has mentioned, I had the same problem. The original part supplied by Caterham was too long (although the diameter of this part was small enough for the black guard). I arranged a replacement (picked up from Brands Hatch during an experience day) but that was too long as well. I eventually let Caterham fit the correct part when they took the car back for the post build check. The diameter of the new part is too great for the guard, but the surface temperature isn't that great, even after a long run, so no problems with burnt legs when exiting the car . Here's a picture for reference.
My car is a Roadsport SV with the 2.0L 175 Duratech engine.
Regards, Ian.
Edited by - IanW on 29 Dec 2009 17:32:54