You do know you have to disassemble the doubler to install it right? You have to feed the allen screws into the clocking ring attached to the main case through the face of the open crawl box. Just in case you need some instruction here are some pages I had bookmarked already for when my kits come in.
http://www.rrorc.com/forums/showthread.php?t=28480&page=2
http://www.pirate4x4.com/forum/showthread.php?t=487225
I'll try and not take that as an insult lol. yes, of course I know it needs dissasembled to mate it to the second case. I figured I'd put it together when I took pics so people could see what it is rather than a bunch of parts.