Reduce nose dive under heavy braking

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Hi guys need a bit of help here,

During autox events whenever I do heavy braking I notice that the rear end gets very loose and unstable. Since I have installed coilovers it has gotten better but I still would like to reduce nose dive and increase stability if possible.

I understand that one way to fix this problem is to up my front spring rate but I really don't want want stiffer springs up front. 750lb is already rough at times, lots of potholes where I live. Is there another way to gain stability by adjusting ride height,toe or reducing rear spring rates?

Here is my setup incase this helps:

custom valved konis with 750lb springs up front and 600lb (might be too stiff) springs in the rear.
-1.9 degrees camber front and -1.7 degrees camber rear
0 toe front 0.16 rear
Car is corner balanced and has a ride height of 27" in front and 27" 3/16 rear