Yamaha DTXpress/DTXplorer/DTXtreme

I have a DTXpress kit and it has a very small kick pad. Is it 
possible to somehow attach another pedal to the shaft of the existing 
pedal or is there and double pedal configuration that will work? I 
read in a very early post that someone made a larger pad using the 
existing tower and electronics. Has anyone done this?

Thanks, Ken