Looks like a really good start.
keep in mind your helmet much be completely behind the forward funny car cage bars. With the seat that far forward, your funny car cage is gonna have to be very deep/far forward of the main hoop.
Our baseline dimension for the inner funny car cage bar is approx 13" from the main hoop. That's with the seat against the main hoop and this makes the helmet just behind the forward funny car bars. Your gonna need to add to that 13" the distance of that seat brace which my guess is between 5 to 6 inches.
Good luck with the rest of the build, looks great so far.