Yamaha DTXpress/DTXplorer/DTXtreme

Hello!

Just bought DTXpress III Special Set. So far everything is great!
But still…I am wondering about upgrading my kit with additional pads. 

So is this possible… Since the inputs for tom 1,2,3 are stereo inputs 
with pad and rim sound or L : trigger input, R : rim switch, is it 
possible to use a stereo cable and splitter for left and right channel 
and hoop-up two single zone pads into one tom input. So that left 
channel would be pad 1 (tom 1) and right channel would be pad 2 (tom 
2)? So that I can actually plug two single zone pads into one tom input 
(tom 1 or 2 or 3) and have different tom sounds on the two pads and one 
free tom input?

I know that I can add a pad on 9/10 input but still…is it possible as 
described?

Thanks in advance!