ORIGINAL: Fiend

when I was building mine (small predator) someone told me not to bother too mutch about the weight, I think that mean light dech without internals (my thought) as for example mine boat weighed les than 300g empty and about 800g with hardware, engine, esc and li-po... so I think You can put as mutch weight that makes power as you wish and the bigger "power" density the better.
besides I run 5070 rpm/v feigao S motor and it works great in my aplication on 2S li po. I used y531 x632 props. x62 was really fast.. the crusual thing is to choose good esc and batteries ir you want to go really fast