Street racing can be safe, obviously some people dont understand that and think nothing can happen at a track (if ignorance is bliss comes to mind) Ive been around street racing and ive seen cars with a backseat and cage and they pass tech, but they dont have a design like yours, they make the passenger(s) crawl and worm their way into the back:toothy7:
Id run the bar all the way across and if people want to ride, they can hash out who is crawling through the jungle gym. Good luck with the cage