I am still running my SP12M out of the box, it's working great. I only run modified outdoors and it is always handling pretty good.
Some points to consider below.
1. Tyre choice is obviously important, depending on the grip I only use Corally Gold Front & Rear. Or Silver Front & Rear. If you are racing stock on carpet I'm not sure, probably silvers as they are a bit harder.
2. Keep an eye on the ride height, you want about 4mm all round. Your kit should have the adjustable axle height and the shims under the steering blocks.
3. Make sure the diff is in good condition, definitely not notchy and not too loose either. As loose will ruin it quickly.
4. Make sure the rear end is not tweaked, there are some adjustments on the t-bar near the front. Make sure your motor wires don't bind anywhere.
5. The Medium or Hard Syrup in the damper pod works for me.
Hope this helps.
PS. I will wait until they produce a battery strap for the "X" version before I buy one.
Regards,