Tinkerbell,

You'll certainly benefit from more chassis bracing, you can read why in general here. http://www.whiteline.com.au/faqelse01.htm#Chassis and strut bracing . The heavier the spring and swaybar rates the more benefit to be found in a stiffer chassis.

However, and with all jokes aside, I would bet you a set of springs that you will go faster at with much softer springs than you have now. Camber settings are probably OK as you can generate enough grip with those springs to compress the wheel adequately need more more neg camber. Also, try some toe out on the rear, say up to 1.5mm total toe out.

Cheers

Jim
Whiteline