The Sit Ski (or Monoski) that I use is one designed by Kevin Bramble , there are many makes available but after using one for some time in Colorado I felt more comfortable in it than any other I had ridden. The choice of Sit Ski is up to the individual rider, but different ones give different results. Some are better for technical disciplines and some are better for speed disciplines. My Bramble isn’t know for the technical disciplines, but with my injury being so low and still having some feelings in my legs it's the best for me.
Unlike skiing or snowboarding where your feet are strapped to the ski or board, when you ride a Sit Ski you are strapped in to the seat to the waist. I have a low break to my back so I can get away with a set of straps that only go to my lower waist, but if I had a higher break and less movement I would be strapped in much higher.
I did find that removing the normal snap in clips and replacing them with snowboard boot bindings was a great idea, it means I can tighten or loosen myself in the seat with one hand.
Your legs are secured in to the rig as well, and I made the same change to these straps as I did with my seat straps. The snowboard bindings work really well and don’t suffer from the problems that my old straps did. Sometimes we get to the hill in the morning and its -20, the plastic gets brittle and just breaks, not something you want to happen at the top of a slope.
Being securely fixed in the Sit Ski is great when everything is working as it should, but at some point you are going to crash and at that point you continue to crash for a while until everything comes to a halt. Padding and a good helmet are a must!