Is this to keep bad things from the engine bay out of the cockpit or just to block the forward air flow from the rear?
Can you lay the top of your template back? Say 45 degrees or more? It would be like a 1/4 to a 1/3 engine cover giving you some protection from the engine compartment with better air flow.
I think straight up, it's going to pull the air up from under the car from behind the firewall and also work like an air brake. It would be a lot of air being pushed over a wide area causing a ton of drag.
Purely on a looks basis I think cut it at the belt mounts.
I had to go back in your build log and saw that you are running a full height windscreen. I was thinking you weren't running a windscreen.
Yeah, go up to the shoulder belt bolt holes as Graber mentioned.
Is it in the EMod rules about the cover or seperation?