was just at walmart this am they have a few sized waterproof camping boxes 1 made for cell phone easily drill holes in it then run wires out and silicone em up. boxes were like 5 - 7 bucks i picked one up for my insane gen 2 hydro for servo box. but usually the hull should be water tight . providing you dont have any leaky cooling parts like lines and jackets etc tape up the hatch but the more water proof the better cuz you never know. esc should mount directly behind the motor and batteries will lay to the left and right to even out balance. then pretty much rx can go in between the steer servo and esc the further away from esc the better so you lessen the chance of any glitching. the higher the better too if you have a antenna mount somewhere . theres plenty of pictures of the insides of monos all over the place google it.