Keep in mind if you can install the LT and ST equally, you should know and consider that they have different adjustment weight 'ranges' in addition to travel. The LT can be 'tuned' in smaller increments 100-120 lbs,(with optional white elastomer),120-140, 140-165 and so on. The ST is 100-140, 140-190, and so forth. The LT also has a preload adjustment that the ST doesn't.
Also, imo, the ST is easier to change the elastomers, jic you need to do that.
The LT tends, after a lot of riding, especially if the rider is heavy(which probably isn't your case), to get a little wobbly. But Cane Creek with fix that for you usually under warranty, so keep your box and reciept for shipping back to them. (btw, I've owned both, the LT on a hardtail mtn bike, and currently a ST on our tandem.)
If you buy a used older model, some don't have the adjustment knob, (#8), which makes installation SO much easier, so keep that in mind.
You'll also most likely have to buy a shim, unless you have the 2 sizes of seat tube on your tandem that CC matches.
If you ever plan on using a seatpost mounted rack, the ST will have more post....
Take a look at their installation instructions on their website.
http://www.canecreek.com/images/stor...ts/thud_3G.pdf
Have fun!
INDY