Adding pads to a SD3 kit?

Is there a way to add pads to a kit, in addition to the default ones? The idea is that I should be able to add enough so that I have access to say, six toms, instead of three. Now, I know you can right click and select from a list of things pre-assigned to that pad, but that isn't what I want. What if I want a double-kick kit?
 
How do I do this?

I haven't found a way to do this. I want 2 or 3 crashes instead of 1. The only solution I found was to add them to the little multi pad that the kit has.