ORIGINAL: Wolfpackin
I found balancing the blades before installing them makes a big difference. With balanced blades my CX2 hovers in place like a dream.
Also I've found that yes, heat effects control. During a long flight my trim tabs can move from one side of neutral to the other. I try to cool down at the halfway point of a battery, around min. 5-6.
Replacing the stock motors with Xtreme 180 ball bearing motors solved my control problems. My rudder trim stays rock solid through an entire pack.