I have stated this before, when I run my 4cell Epoch on a double charge it runs shy of 10 minutes. I can feel that my motor case is getting warm after that. I usually let it rest a tiny bit. If you use 210 mah, you may not want to let it run the whole time, or you may burn out the motor.
I don't know how much heat they handle. Mine don't get REAL hot, but I am anal.
About the 6degree turning...
The Radio Shack 1/43 scale Viper is a DGmaster. It just has the Viper shell. It is virtually uncontrollable at high speeds. (unless you're just cruisin' around) It's hard to keep it on a track.
If you want a comparison and explanation as to why the DGmaster is not truly fully propo, and why it sux compared to the Epoch, click
HERE