Maybe crazy, but can suspension be softened?

[Bart Carter]

Actually a stiffer front than rear sould increase understeer and decrease oversteer but that said- I think you have solved step one, new tires! Your car looks great.

Agreed.

If you go to a softer spring/shock setup, you will probably need stiffer swaybars on the track.

 

[Jason Watt]

Actually a stiffer front than rear sould increase understeer and decrease oversteer but that said- I think you have solved step one, new tires! Your car looks great.

In many cases yes - but I feel that the original understeer was due to too much roll at the front, so now at mid/exit corner the harder spring decreases what I would describe as "roll-understeer" at the front end.
A stiffer rollbar (you Yanks call it swaybar I think.. ha ha) would also help a lot.
My new tires is for sure also a factor because the rears are a shitty SUV tire (Yokohama didn't have the correct 22" size in a proper model tire) where as the fronts are the new ADVAN Sport that works very well.