Transparency issue on iOS

I have included a chicken wire fence in my app - a basic 4 quad mesh with a Mobile > Transparent > VertexLit shader. It seems to slow things down (I tried it with non-transparent and things were faster). I would like to use it transparent, so is there a chance I can speed things up by breaking the mesh into 4 separate quads, so that from inside the fence (where the camera will very often be) only 2 or 3 of the sides will be seen? Is it calculating alpha for the whole mesh or just the parts onscreen?

The vertices off-screen have to be processed, but not the pixels, so what you’re suggesting should be useless. I think your only solution is going to be to run at non-native resolution if you have one of last year’s underpowered models. All iOS devices from 2010 had GPUs with unacceptable fill rates.