This one is a bit different though it appears as Dave said in his opening post "Please note that i have 'taken a flyer' and the model is now in cad/cam stage and i am really hoping that this is completed so i can get 3D resin prints on display at the upcoming Warley 2017 show (no promises though)."
So the cads already started, meaning the research has been done, meaning the discussion on what diagram Dave should do is irrelevant as it's already been researched and cad started!
Perhaps we should focus on what scale he should do instead (n gauge please )