Attached is a very hastily modeled assembly of the center goal structure. It’s as accurate as I can reasonably make it working only from FIRST’s blueprints.
I looked up the dimensions for a 1" PVC Cross and 1" PVC Tee and modeled those parts to match, but I can’t assure anyone that their overall dimensions match what FIRST is planning to use.
I cheated on the netting. Y’all can make it look more like netting if you’ve got a lot more free time than I do. 
Edit: Fixed Spin Bar height on model.
FTCCENTERGOALASSY_R1.zip (739 KB)
FTCCENTERGOALASSY_R1.zip (739 KB)