Shouldn't say really I suppose but I'm a bit daft that way....make a splash mould of the centre about 8" wide then..cut the nose in half and sit it on your chassis then with the splash mould you have a guide stick to fill in the gap and you have a nose that fits the width...may not be deep enough so you will have to fart about with that with foam/filler etc
The above is nowt new that's where a lot of the 7 type bodywork comes from unless you start from a block of foam...
As the meerkat bloke says it's "simples" but time consuming and will no doubt cost a lot more than buying a ready made one....but you will have made your own.
I dabbled with carbon but it's too expensive to play with and make mistakes only to have to chuck it in the skip so I don't bother anymore.
The only Caterham bits that will fit will be wings, the nosecone is skinny weed thing and not deep enough and also has a rounded section where it meets the ali side panels.
Could always buy my moulds....