What will be the weight of the craft? Or how large physically do you expect it to be?

I'll bet you'll need like a 2500mA 3-cell for the vertical and maybe a 1000mA 2-cell for the controls for a 24" diameter craft. Just a guess really.

I bet you'll come out ahead putting the vertical fan on the throttle stick and a single pusher fan on the elevator stick steered with a servo on the aileron stick.

I know you can run the ESC off the elevator (or any stick for that matter), but the stick centers with a spring, so you'll either have to open the transmitter and remove the spring or setup your trims so center stick is OFF-motor...... OR I hear they have reversible ESC's for the 4D fliers. Center stick is off motor, forward stick is motor pull and back stick is motor push. That way you'd have reverse on your hovercraft!