John, there should be a slot in the fuse, maybe its under the covering? The elevator and horizontal stab both go in the same slot. Slide the elevator in first then the stab. Below is a diagram of slot shape.
Btw: I am going by memory on this, its been a year since I had a Topcap. Wgeffron, can you confirm this?

hope this helps.

I also have an Aeron on the way....cant wait!