I'm thinking they were giving advice of springrates as if they were in the OEM location which is why they said 9kg springs were the lowest that they recommend.

 

I think you will have oversteer issues with your 14/9 setup but there are other things you can do to correct that but I would start with different springs

Ways to Correct Oversteer

Lower front tire pressure
Raise rear tire pressure
Stiffen front shocks
Soften rear shocks
Raise front end
Lower rear end
Install narrower front tires
Install wider rear tires
Stiffen front sway bar
Soften rear sway bar
Reduce front negative camber
Reduce positive caster
Stiffen front springs
Soften rear springs


Ways to Correct Understeer

Raise front tire pressure
Lower rear tire pressure
Soften front shocks and stiffen bump
Stiffen rear shocks
Lower front end
Raise rear end
Install wider front tires
Install narrower rear tires
Soften front sway bar
Stiffen rear sway bar
Increase front negative camber
Increase positive caster
Soften front springs
Stiffen rear springs

 

This is what Adam confirmed to me: "Its a special damper in the back to take the rate. Its valved for those kind of rates. Its a true type rear with swift springs"