XRAY - Model racing cars

Just so I think I am reading this right. For an asphalt set up with the new 2mm chassis one should do the following:

1. put o.5mm shims under the arm mounting blocks all round;
2. should have around about 3000wt oil in the rear diff
3. go softer by one grade on the spring all round ie 2.8 now 2.6.

I apologise for the slight vagueness to my question, but when i had the t3'11, I came to my own set up that was somewhat removed from what was the common set-ups ie. I narrowed the front track by 0.5 each side, lowered the front a-arms and put in a tiny amount of anti dive. I also used HPI silver fronts and blue rears.

Another question - I have just bought the t3'12 main chassis (my old t3'11 one was tweaked). My old top ddeck was not damaged, and I wanted to know if it is going to be night and day difference changing the top deck to the new t3'12 one, or is the old one perfectly fine?