Interesting points - good for mulling over.
My reading of late has me looking at the rear end of my car to assist the front - sounds strange but aparrently true. I have a picture at my last OP supersprint which shows it perfectly. Leaf sprung live axles have roll understeer built in by the manufacturer and fortunately there is a simple cure - I'm hoping so anyway!! My car is suffering from a bit of diagonal transfer with an outside rear taking too much load and unloading the opposite side front - so what can appear a front suspension issue can be actually a small problem being magnified by another - in this case, the rear. Suspension is rarely a black and white science so read up and ask questions because everyone has a theory
I agree that 6 deg neg is a little steep - 4 to 4.5 would be max I have been told.
Driving style is another indicator as pointed out earlier - and if you have a locked diff. If you do have a locker, you will either be braking, on the gas, or understeering - go or stop - if you don't DRIVE through corners with a locked diff the diff will tend to drive you
Hope this thread continues - will be a good learning tool for everyone.
Cheers