I have a set of these Forge Carbon framed ones in the attic, they are the older 76mm ones that Litchfield fitted to my car when I went stage 4 some 2.5 years ago. 12 months ago they swapped them for the slightly larger 80mm units when I went to stage 5.
They were fine for stage 4 then, check with Ian that he can still use them given mapping has moved on. I guess they would still be fine for a stage 4. Let me know if you are interested and I'll dig them out.
Sorry pic is one I nabbed from the net and its not great quality