I run the Mamba Monster X with the Castle 2200KV on 6S and it does well with heat for the size. It's a 4 pole with plenty of torque and speed. I do run a fan and heat sink on 6S and the setup has a hard time reaching 140 F with a 12 tooth pinion. It's plenty fast !!!! That setup works well on 4S, 5S and 6S. You just have to gear it properly and on 6S, you might need some cooling. Without my fan and heat sink... I can get it up near 180 F with a 12 tooth but it takes a while. 5S should be much cooler. With 5S...I don't see many battery options but they are out there. Look into the Max Amps 5S battery and their battery tray metal insert. (expensive but nice) Pair that with a Castle Mamba Monster X,, the data link and a 2200KV motor.....that thing should run real nice and decent temps. Note: the Castle motor does not bolt in very easy....it has smaller screws than stock. You could find the stock motor for super cheap and pair that with a nice ESC on 5S and gear it up....It will bolt up very easy. You just need 6.5mm bullet connectors to wire it to a Castle Mamba ESC and some silicon wire. The stock motor should rip nice on 5S...maybe a 15 or 16 tooth pinion on it.