I'd have to agree about the system charts. For your DSLR you'll need the CA-35 wide mount adapter plus a T-ring specific to your camera. Claude can advise you and supply them. The TSA-120 originally ships with two 50mm extension tubes that screw into the 2.7" focuser and one will probably be needed to bring you to focus. Did you get these with your purchase? (I have a spare if you're interested). I'd recommend getting the CAA (camera angle adapter) which makes rotation for object framing easy without changing focus. This also adds a bit of length to the system.
With CCDs and the flattener or reducer, the system is more complex and you need to take into consideration the back focus of the accessory and the distance to the sensor plane. Here's a photo of my reducer setup which includes the CA-35 and the camera angle adapter. The extra bits to the right of the CA-35 are specific to the CCD and filter wheel you use.
http://www.pbase.com/rigel003/image/132410762
Lots of good info in the attached chart from Texas Nautical Repair (Takahashi America).