I know you snagged the trailer, but I wanted to follow up with this in case anyone else had this question in the future. I have been very happy with the Cascadia Vehicle Tents customer service, and following a shipping snafu at Cruise Moab, Bobby from CVT even delivered by annex personally to my house. However, after I started installed it, I feel like maybe it was a waste of money. I have a Mt. Caylee/Mt. Bachelor which is the smallest tent, so there is a possibility a larger tent might be able to fit my needs. The CVT website has ZERO photos of the insides of the their annexes, and absolutely no information about them other than price. So, I was left with a few hundrew dollar gamble that it would work out, and it just fell flat.
Here are my gripes, and they all relate to the design of the back wall (vehicle side) of the tent:
1) The rear side attaches to the bottom of the RTT using the slide slot that the cover uses. So, all the enjoyment you had putting that on when you installed the tent, well now you get to enjoy taking off the cover, sliding in the even larger annex, taking off the annex, and sliding back in the cover. Each and every time you use the annex. If you are like me and think, "maybe I can just leave the annex on...", no, you can't.
2) The rear door of the tent does not extend to the sides of the tent, so there might be a small vehicle that has a square rear end that would fit the annex, but the rear door flat out needs to be wider to be able to create the Double Decker Dirtbag Hilton I had envisioned. I would think this setup would be the primary function of the annex. Being able to cook out of the elements, leave the back of the truck open to either sleep or gear access. However, the designers had some other use or application in mind, which unfortunately falls flat on its face. As you can see, it is possible, but leaves a massive gap under the bumper, which would make using the floor impossible. Bringing me to my next point.
3) The door zips from the bottom up. This makes sense on every other door, except this one. Every vehicle has a gap between the bottom of the car and the ground. IF the tent zipped down from the top it would be possible to seal the gap between the two and leave it open. I can't imagine the scenario where someone would actually be walking through this door. Easy fix, but in my opinion it was just poorly thought out for the actual application.