RE: Will This Work (Big Newb Here!)
Let me add to the above answer. Your choice of esc WILL NOT work because it is only rated at 9.6 volts maximum and a 3 cell lipo will be well over that.
A nimh only esc will "work" with a lipo, but your low voltage cut off will be way too low. If you were to fly too long, your battery voltage could possibly drop to battery damaging levels.
The esc you will need must be able to be set for lipo battery cutoff voltages AND it must be a brushed motor esc since you are using it with a brushed motor.
You will find that with a 3 cell lipo, your 400 brushed motor will work very well with your Slow Stick.
Keep in mind that someone MAY tell you that you can't use a 3 cell lipo with a Slow Stick brushed motor. Well, that may be true with the 350 motor, but the 400 can provide a couple hundred flights or so with no problem using a 3 cell. I finally put a brushless motor on my Stick at over 200 flights and the old motor is still being used by a friend of mine on his Stick.
Cliff