Man it depends on your turbine.. If you turbine has a battery voltage cutout voltage, I would NOT put anything on the turbine battery. If your turbine has a low voltage run no matter what settings like Xicoy ECUs, then you can put stuff on the ECU battery like smoke and gear. Since you are runnng a 3S turbine, any regulator would work, but you will have to figure out how to make it not powered when the jet is just sitting around.
If it were mine, I would convert my turbine back to 2S pack, and then use a Y Deans Adapter off the ECU pack.
You can also tap ONE of the receiver packs.. it will be ok and work fine.. The spekky powersafe receiver will use the other pack when the voltage drops.. there wont be 50 mah difference.
I have done it both ways.. so it really depends on the ECU IMO