Ride quality even worse than expected. Advice welcome.

Not at all...a flexible chassis acts like a soft spring...

I totally agree. However I have always heard that one reason for the lack of connection between the front and back of these unibodies was for a more compliant ride. No, I don't have a source on that...just tribal knowledge, I guess. Maybe that was just an excuse for cheap-o chassis design? In any case, they obviously didn't plan for the grip capability of the tires we have today.