ok i took Ole Tobiesen ford pick-up ( on Acknex site) windshield was a seperate model from the pick-up

I merged the 2 models togeather, gave the mdoel a second skin and grouped and UV mapped the windshield triangles to the second skin. then appleid a 30% transparent green image for that second skin ( original skin of the model was untouched)
now its all in one model vs needing to script attach transparent parts to opaque parts.
a full opaque image with 100% transparent parts in the same image seems to work fine. engine just doesn't like the full opaque and semi-transparent in the same image.