This is the GT base with a 55" 996 cup wing.
The width is perfect, you have to make the uprights and the base Thales some massaging to get it to fit but the downforce is worth it. I've run the 3.8 tail, but it's heavier and doesn't give the same downforce. I don't have any real data but it seems like much more drag with the 3.8 base.