I kinda knew the answer already. Just needed someone to validate my dumb move. The fabric I got didn't have any markings on it whatsoever and I just unfolded it and went to work. I pulled it up shortly after I posted and re-installed it using the Simonis printed instructions. The printed instructions kept referencing maintaining the proper margin but offered no guidance on making indexing marks. I just ran a light chalk line a couple inches back from each edge and used that to get the stretch evenly. It's definitely tight and I don't seem to have any of the stretch shadows I've seen talked about here.
Here in Alaska we are pretty much on our own and if I ordered the DVD's they'd likely arrive after my Halloween party in a couple weeks so I just went for it.