With that big a difference between the big rear bar and the front stocker, plus the wagon's extra weight carried high, and a little more flex in that rear wagon structure, I'd expect the oversteer would snap in pretty abruptly at the upper limit of cornering.
With the right balance of upgraded components, as illinipo details, a small wagon can become a fun handler. That's how my Escort wagon is set up, but I've replaced endlinks and added polyurethane bushings throughout as well.
All my relations, Christine
NW Posse #17
"Straight roads are for fast cars. Curvy roads are for fast drivers."