I noticed the same thing when I ordered the Trailex for my one TI. The trailer that arrived said SUT-200-AI (indicating it was for an AI), but the boxes contained the longer front crosspiece for the front TI cradle, and the T-bolts were also for the TI cradles. I noticed that on the outside of the box someone had scrawled the word "tandem" in black marker.
As of this writing there are no instructions on the Trailex web site (or anywhere else) for building this trailer in a TI configuration. As such, I built the trailer per the instructions, and it seems to work. However, I noticed in the Hobie catalogue that the photos of the trailer show a slightly modified build from what the instructions indicate. Curiously, the Hobie build appears to violate the Trailex warranty as stated on a sticker on my trailer's tongue. I don't know if they simply disregarded the warning sticker, or if the pictured configuration is the actual TI build for the trailer.
I've been doing some web searching and there is a wealth of info on this trailer when used to carry a Sunfish. That trailer is called the SUT-200-S
Here's a tip: I saw on some of the Sunfish forums that they recommend torquing all T-bolts to 30-40 foot-pounds.
Trailex offers some options & accessories for the SUT-200-S that are applicable to the AI & TI trailer. Here's the link:http://www.trailex.com/SUT-200-S.cfm
I ordered the spare wheel (already have a lockable mount), a second set of tie-downs, and the bearing buddy set (at the recommendation of a friend).
I hope this information has been helpful.