The Altai Hok 145 cm ski-shoe, a bit of snow, some sturdy boots, and you are having fun. Compared to the 125 cm ski-shoe, the 145 floats on top of the snow more, both ski-shoeing uphill and schussing downhill. Versus the 125 cm, the 145 ski-shoe also has more leverage against the snow with the tip and tail, as more of the ski-shoe is sticking out from under your foot, so there is more to lean into. As the telemark/ cross country style bindings are only connected to the ski-shoe at the toes, leaning forward is not going to have a successful outcome, but as an alpine and telemark skier, I have always skied on longer skis, so I was comfortable with the longer pair immediately and found the fore-aft balance point of each ski-shoe easy(ish) to stay above.
For a person who might be eager to go slightly faster on the downhills, the 145 cm is a good choice compared to the 125. The 145 is also a good choice if you are going to be trying out telemark style turns, as it works more like a traditional ski than its shorter sister, the 125. So, for those who want to make more turns across the slope, or zig-zag through tight woods, the 125 gives more maneuverability, and easy use, but the 145 is going to work more like a traditional ski.
I mounted the universal binding on the 145 and used a pair of snowboard boots to test them out. The snowboard boots are fairly stiff, although they are just foam rubber, and thick fabric and canvas, the laces make them snug and give ankle support. I recommend a tight fitting and supportive boot such as these for best results. I also have a pair of telemark bindings, which I then can mount onto the 145 Hok ski-shoes with a screw kit ($19.95 on their website), and then I can wear my Scarpa Terminator telemark boots. The Altai website has two telemark bindings (3-pin and cable) that come with the screws you need, and telemark boots available so this is an easy path to follow. The telemark binding/boot provides the most rigid connection to the Hok ski, and the most effective edge control and input from my feet to initiate and complete turns. I am looking into whether the is a pair of bindings that have the right hole pattern for the toe-pin alpine touring boots, which wold be a third option, and very rigid. The more rigid setups could overpower the skis (especially the shorter ones), so the universal or telemark set-up might be all you need.
The thing I like most about both these ski-shoes (the 145 and the 125) is that they function like a modern snow-shoe, but without the need for the wide track stepping needed to get snow-shoes past one another while walking. For this reason, I can ascend, traverse, and generally move about outdoors in the snow with a normal walking stride. This goes for both sized ski-shoes, because they are long and skinny as compared to a snow-shoe with their wide platform that makes people take wider steps. That ease of walking, plus the ability to slide on the downhills make these the best way to get around in winter! After all you walked up that hill, you deserve to have some sliding fun on the way down.