It seems my suspension behaves quite nonlinearly. It is hard to describe but here's a try:

When I corner 'lightly' it is soft but when I drive Hard it is radically different. There seems to be a distinct point as the car settles into a turn that continued increasing force translates into much less travel. It makes driving kinda unpredictable. I don't think its as severe as hitting bump stops, and the GC springs aren't supposed to be progressive as I recall. I noticed it yesterday in the mountains near Malibu on sharp turns, but it happens also at the track, the few times I've been there. I can't remember the same thing on stock suspension.


What is going on?
Am I insane?
Is this typical or is something weird going on?

I have Ground Control / Koni setup, corner balanced, and lowered only 5/8" or so.

 

Shocks are by design speed sensitive and vary their damping force based on piston speed. Hitting bumps/dips and transitional maneuvers will create different piston speeds resulting in different damping forces. Faster transitional maneuvers will do the same thing, so yes, things do vary. I've always found the Koni yellows to have a lot of rebound damping (too much for some spring setups ppl try to match to them). Try adjusting it around to get the damping to a point where it's a good compromise for your style of driving and areas you drive in. Also, springs may be linear, but that's the spring rate. As the spring compresses, it requires more force to compress it further. The amount the spring compresses will determine the energy stored in it which will affect the piston's speed as it expands, thus changing the damping.