I tried butting plates together (either 2 Bs or 2 decorative strips) and got a crease. I put tape over the seam and still got a crease, and the tape left a bit of an emboss on my paper.
Then I had Home Depot cut some scrap acrylic to fit, and that worked with a few cs shims.
I know some people butt plates together and don't mind the crease, but it bothered me. The Big Shot and Big Kick can accommodate the cutting pads for the Bigz XL dies, so I ended up buying one when I realized I was buying a lot of the Bigz XL dies and loving them.
Since then, I've read of the Accucute plates. They do cover the cutting area of most of the Bigz XL dies and fit through a CB. I think this is the one:
http://www.accucut.com/Cutting_Mat5_...ath1,903.html?
It turns out I prefer the BK to the CB and I'm glad I bought one, but if you want to keep your CB, why not try the $5 Accucut plates?