CF trunk lid for PRHT? I don't think so.
As far as I recall, the change to the rear of the car brought about by the PRHT design required that the trunk lid went from aluminum to steel, as it was a requirement to add the necessary structural rigidity (under compression) lost in the changed shape to accommodate the new retracting top.
Being that the steel trunk lid in the PRHT is now an essential structural component, any CF lid would need to provide the same strength. CF is known as a strong material, and it certainly is in tension and where lateral forces are applied, but its ability to withstand compressive forces is not necessarily that of steel. That is a design issue that would need to be addressed.
Given that Mazda reluctantly found it necessary to do this for safety reasons, even with their so-called 'gram strategy', not such a hot idea for either yourself or your passenger out on the road.
My post is that type which is often referred to as 'Party Pooper' ...