Is the Sidewinder capable of 4 A123 cells? (That would be 13.2 volts) I would be using it with a Ammo 28-35-3900 in my Vendetta ST(1/18). I would only use it for speed runs and if needed I could get a fan for the ESC.
On the high side it's rated for 3s lipo(11.1) and 12 cell nimh(14.4). 4s A123 will drop down to 12v under load. At the load level you want to run you should be ok. I have a question of my own, will the sidewinder(1/10) handle 4 cell nimh (4.8v)? I set up my KX1 with a Feigao 13t and a 4.8 volt nimh pack and it wants to cog after it has started to accelerate. The FDR is 4.5 to one. Don