I have never checked the springs that came with the X3 / IGT8. I also have not tried to see if other springs will work. I know IGT8 (RcTarget) is working on doing new shock towers that will use the front shocks also in the rear. This is something that I had done on the OFNA DM1 with good success. With this, you would only have one size of spring, so decrease the cost for more options.
Grenade, I'd really like to experiment with different springs. Can you tell me what springs will fit and what spring rates are stock to the IGT8 as a starting point.