speedworm-
Start with that setup but go 5wt higher all round, so 45wt in the front and 40wt in the rear. I think this will be as hard as you need to go.
Only if the front end is diving in and still has alot of body roll, then go smaller piston; but try it with the heavier oil first.
Mark-
When i first tryed the losi springs on the yoke shocks i couldnt lower the ride height enough. I started using the plastic shock collars and didnt allow me to lower the car enough, so i put the champions pack shock collars back on and the lower shock bottoms on the rear. I had no problems with the springs coming off or the not being centrally aligned.
Hope this helps,
Ryan