We've been running the kit Xray 3 dot front and 2 dot rear both indoor and outdoor with great success on both astro, carpet and dirt on the 2WD.
No need to go out and buy additional springs for the 2WD.
We're still running this spring setup on the new prototype Malin's been running for the last 5 months.
Here's the start setup we use for the XB4 2WD on med - high grip carpet and astro outdoors and indoors:
http://forum.teamxray.com/xform/inde...&setup=xb4_2wd
Bent
