According to this calculator

http://brantuas.com/ezcalc/dma1.asp

At full throttle, you may be asking too much of your Lipos unless they are rated at 10C or better. You are at or over the edge of what the 400 is happy with; you are already pushing the 400 with the 11V Lipos.

Can't remember the specifics, but I recall it is desirable, for longevity, to keep the 400 under 100watts.

For the Slow Stick no need to prop for speed....

Hope this helps.