Help with Ion kit please

[Al9000]

I am considering buying the Ion Drum Rocker kit for my xbox 360 as my wife is sick and tired of the standard drum kit that came with GHWT not functioning correctly. I have adjusted it using the tuning kit but even with the sensitivity turned up full the red pad will hardly register a hit.
My question is this, the Ion Drum Rocker kit appears to have 4 drum pads, a kick pedal and 2 cymbals. Am I being thick, but how does this work with GH or Rockband? The GHWT kit has 3 pads and 2 cymbals. Surely there are only 5 "tracks", or whatever you want to call them, scrolling down the screen corresponding to the 3 drums and 2 cymbals.
Also, from the photo of the Ion kit the drums left to right seem to be colour coded Red Yellow Blue Green. But then the 2 cymbals are coded yellow and blue!?!
Amazon are selling this kit specifically for the 360 so I know the kit must be right, but I just want to get my head around exactly how it works before I part with £250!! It's the curse of being an engineer by trade, I just have to overthink and analyse EVERYTHING!!!! Please help. Thanks,
Al.