Actually, it won't. Removing the shim from under the blocks has by far the biggest affect on altering the Rollcentre. In order of magnitude, from biggest affect to smallest it goes;
Suspension block shims
Outer camber link shims
Inner camber link shims

As an example.
1) Plugging MatJ's current setup into RC3, the rear rc is -4.98mm
2) Removing the lower 0.5mm shims moves the rear rc to -6.11mm (so lower by 1.13mm)
3) Adding the 0.5 shim to the outer link with the lower shim removed gives -5.63mm (so a 0.48mm change)
So removing that lower arm shim and adding the outer link shim will actually still result in a lower rear roll centre overall.

I don't disagree with that the front and rear aren't rolling the same, as the kit settings do give quite a bit of difference between the front and rear roll centre. (-6.16mm front vs -4.98mm rear) So matching them close, as the above settings help to do, will help the situation a lot.

Thanks guys, I appreciate the explanation.

I deffo need to get that RC Crew chief soon!;)

rear diff
 

Is the rear diff suppose to be tight ? I can't pull it apart . I put them together to see how it fit now I can't take it apart .

Did you line them up like you are supposed to with the number and the dot? If so they should come right apart.

Nope .....I just push them together . I can't pull it apart so I guess I better order a new one

They should come apart easily. But if they are stuck, try sliding a flat blade between them, and then twist it to lever them apart.

I have little idea what you're talking about. I do geometry with a pencil on paper not with gizmos (old skool). And I think primarily (I was thinking about this yesterday as I was writing) the amount of change depends on ride height (by the way, what ride height did you use in your running of the numbers? - he doesn't tell us what the ride height is). My point is not to claim that his does more than the other (not sure why you assumed he would go with .5mm shim on the outer camber link either, because he doesn't tell us what he's got now).

5mm front ride height and 5.5mm rear with 3mm on the outer camber link.

You are fine. I did the same thing. I didn't read that part. They will come apart just not that easy. Like mentioned I got an exacto blade in and started to work them apart. Mine is still fine even though I did that.

aside from TQ, where I can find the HPI silver springs?

I got it Thanks

I was able to purchase mine through HPI. But that was a while back. Good thing I ordered 2-sets.

There you go. I'm definitely not a clairvoyant.

If I were you I would equalise the ride height and add antisquat to the rear (a fraction). This is assuming you have that rake to combat squat. This will help keep the weight on the rear better (which is the core of your problem - loose rear end=not enough weight which means less rear end grip). Roll and camber are just instruments to aid using the grip, but if you don't have it in the first place, then that's where you should start. Roll center is actually a fine tuning instrument. It's not going to help much if the grip is not there.

Oh, and by the way, try to have the softest chassis setting, because as I said, the rear end needs to roll more so the chassis should be free to flex to accommodate.

In my experience with the TRF418, the Yokomo style motor mount by Samix transformed the car into an easily tuneable machine. The Tamiya item was just not that good. Now you have the one piece mount on the 419, should be good though it still looks a bit too chunky.

You must have pushed them really hard to persuade them to mate against the wrong slots. I tried with mine, and gave up, it took too much force. Rotating the housings around I found they are actually keyed in a very subtle way. One of the slot-tab pairs is invisibly larger. You can see it if you measure with a good calliper (I think it's a difference of about .02mm).

Noob mistake. Tamiya may be sloppy, but their stuff goes together well, and if it doesn't, then it isn't meant to.

Nope not a noob mistake, just missed it. 418 or any other of the 30 or so kits I have built has this feature.