Anyone mention airbags yet? I think the car has six of them (the four beams, steering wheel, passenger dash). I remember hearing somewhere that airbags and their deployment units are pretty heavy for their size, in general, although I've never handled one.
Let's say, on the heavy side, that they're ten pounds each. Removing the four beams would then be forty pounds off - essentially bringing your car back to 1990's safety. Dropping them all off, say for autocross, sixty pounds. ALL of this above the cars center of gravity.
If the ten pound estimate of weight per is about right (again, I'm not positive), I think this would actually be noticeable in cornering at the extremes.
Just a thought. I probably wouldn't do this myself: 1) Because I don't want the damn things blowing up in my face, 2) I don't know how to wire them to read still present and not give you a continual CEL, 3) accidents, especially with passengers. But, if it were easy to do/undo, I'd at least look into it for the pillars.