William - got a chance to try out the code and it did have a positive effect but I am having a hard time measuring how much of an effect because I did a naughty change management thing and also updated my driver at the same time.
I am finding an increase in refresh time for all models (regardless of whether overlay/transparency is being used or not) after the driver update. LOL. So I now have to run some scenarios to reset my baseline with the new driver. But I have be able to show a positive improvement with your material definition.
I am going to guess that whatever entity is completely filling the screen in the last shot has alpha transparency on? Is there a reason for that camera to be there? It is an odd shot.
I found another thing that effects refresh times for my configuration is tga skins. TGA skins seem to put a higher demand on refresh times than say a pcx skin with overlay.
I am not claiming it is 3dgs' fault. Do any of my posts sound like I am saying it is 3dgs' fault?
I am trying to optimise for lower end cards. So every little bit helps. And the problem is just less of a problem without tga textures. And some of the others posters indicate having seen the same problem - so the information is for those interested.