it sucks. jumping on a tramp flat footed sucks enough but then withe ski boots and skis you get like 4 feet of air and can basically do like 540's and sketchy backflips and lincolns. you never get enough air to even really do grabs.
the best thing you can do if you want to practice tricks with grabs, is get the like pipe padding stuff and some light, stiff material and basically duct tape it in the tip and tail, leaving about a foot in the middle hollow and make like an ankle sized opening for your foot. it is stiff enough not to bend in fast spins and to kind of hold grabs hard like on skis, but it is still light and your ankles can flex fully.