How do I put these parts together?

[Ryan]

Hi guy's,

I'm in the process of putting the rear body and the birdcage back together.
My problem is, that I've tried to do this last weekend but the tunnel at the rear body won't enter underneath the tunnel at the floorpannel. It seems to be too tight. How do I proceed. I can cut the front part of the tunnel at the rear body, but I prefer to do the things the way it was intended to be used.

Any help,

Ryan :confused