Wease
I'd try lighter fluid in the rear not thicker.
Thinner fluid
• Increases cornering traction • Increases steering into corner
Thicker fluid
• Decreases rear traction while cornering • Reduces wheelspin
Are you running sway bars?
After removing the plastic chassis spacer and setting arm spacers, I didn't notice any handling difference with my 13 car vs the the 14 car I have now.