Tandem,
I can only repeat myself, I not suggesting "simply reading across" or planning to break rules, faced with a choice:
balanced against the alternative risks and the aircraft's known record in icing conditions ie did a previous mark have a clearance down to -6 deg and had there been changes made that would affect its performance
Ah, Stn Cdr Odiham didn't recognise the technique, just remind me of his vast Chinook experience again?