Viper,
You worked with Calean (tyre textures) on your 3d rims & he has already produced what I think are the best cockpits for GP4.
Why not colaborate with him on this. Surely two heads are better than one in this instance as I think Calean is trying to improve his at the moment to make it even more realistic, i.e. lowering the cockpit in relation to the front wheels (as per your Williams picture) etc.
Good luck however you proceed as I feel very strongly that the more lifelike the cockpit can be made to appear is one of the most effective ways of improving GP4 as it is capable of producing stunning visuals, as your cars show!