Ah .... er ... (cough cough)....
Sorry Kurt! Got it right this time
What had happened was this - in order to get the prop control working okay in the sp2a single engine slot I did some sleight of hand in the exe which gave both the e.3dz and g.3dz transparency capabilities. I also had to make some slight ammendments to the 3dzs of those parts of the model. However, I named the skinfiles differently and so the model was picking up the old skinfiles I had for the e and g 3dz.
Now all is fine. The evil falling down water has been locked away.
I can be so thick sometimes!