Lowering the rear ball stud helps a lot. How have you got yours now as the Instructions are a little bit misleading and I have seen a lot of people runing one washer under the top deck and one washer which isn't right it should be two under the top deck.
Stuff your doing sounds a bit like what I did with mine, I went to silvers all round, stiffeened up the oil and also put some extra spacers inside the shocks to get rid of a bit of droop and also stop the driveshafts popping out.
I race on full carpet and mine seems to be great, although I am running staggered ribs on the front to save my tyre budget
. staggered ribs have only been a recent additon though and I was running full minispikes all round it was nowhere near twitchy.
Ps I am running full lock on my transmitter and the curve is set to 0%, so linear.