Since it is a race car, if my memory serves, all the 4WD cars come with the LSD. But they are set equally. this gives the front wheels as much "say" in the direction the car is going to go as the rear wheels. Resulting in MASSIVE understeer and the aforementioned "crashing into walls".
Set the LSD with the front at 5 15 5
Rear at 10 30 10.
From there its a matter of playing with Ride height.
If the car is still understeering horribly and you've got it "in the weeds" raise the back end 10 clicks. Then take it on a test run and see what you've got handling wise.
If she's still understeering raise the rear another 5-10 clicks, and keep testing until you're happy with the handling. TCS is not really the answer for 4WD cars. It is however, a lifesaver with both the Speed 6 and the Speed 12.
Set Brake Balance at 20/15. and if the auto/wide slider is above 16, slide it back. Yes, your top end will be affected, but you'll actually be able to reach it.
Hope that helps.
BTW, you can use the same settings on All of the Racing 4WD Skylines.