[Graham Boak]

I think you should be looking for an OR, Operational Requirement, rather than a Specification.

There is an Air Britain book that deals with such things, which I'm sure I've got but it appears to have been a victim of the recent re-organisation of the hobby room and I'll have to wait until it resurfaces again. (I'm still missing four models...) Possibly it will have been too late for the book: in which case it will have been covered in a series of more recent (but now unclassified) ORs running in Militaria (as was).

Sorry I can't be more helpful at the moment.