Go to
www.atomicmods.com. Rob has alot of pictures of the board. If you look around, you might even find a drawn out schematic of the board. What part of the board are you interested in? The ESC?
Here's a schematic of the stock ESC. This, folks, is what an h-bridge is.
This schematic is true to the parts references on the xmod board. The DC voltage sources are replicating the pins of IC1. I did this to simulate the circuit and test its functionality. The box looking thing in the middle "xmm 1" is a multimeter. I used it to replicate a motor to test the changing states of the voltages and currents. This is your ESC.
I have a design of my own that should be able to handle 20x's the power as any h-bridge possible could with the small 8 pin IC's. I'm going to use TO-220 power FET's and restructure the circuit a little to make for better FET driving. There has to be a level shift between the weak 0V to 3.5V PWM signal and 16V+ DC. So you need to encorporate driver transistors to help fully turn the power FET's on and off, with a little help from the very power that they are switching on and off to the motor. A little pre-amplification, if you will.