Sit-skiing is one part of disabled skiing. Amputee & Blind skiing is easy to start with the Triple Bar. Amputee's should use the Largest ski available. For example, jump skis work very well because you need a large surface area.
Blind needs a lot of dry land instruction. Let the student "feel" the correct body position of the instructor, then make sure their body is in the correct position on land before they are in the water. Make sure the skier understands the "squat position" this is very important. Again large skis work the best. Yo use a small bar that connects the tip of the skis so the skis are stable.