.... and I don't dispute that it's there for a reason. The problem is, you're falling into the trap of adding a cage bar for the simple reason that a completely different type of car uses it.. and you can't explain why.

Let me clarify what I said before. In Improved Touring, with our restricted cage rules, I can think of several bars I'd rather add before I got to adding a diagonal across the windshield. If all of those bars were added, and I thought there was still some improvement possible, and it wasn't obstructive to the view, didn't push weight up substantially, was able to cleanly tie it into tube nodes as well as deal with the dash/driver/column/heater core etc issues, I'd consider something similar.

I've never actually looked at the SafeRacer cage to see what the bar ties into, but depending on the roof bar setup, this looks right up the alley (bottom pic)