The Shamans max out at 173 because they're a way fat ski. Trust me, you wouldn't want them longer. They're 160mm at the tip. Because they're short and fat they excel in deep snow in trees. Hands down the best deep snow tree ski I've ever been on. The first time I was on them I couldn't keep from giggling and laughing I was having so much fun.
I know people that have tried them and don't like them though. Some complain they are hooky in deep stuff and if you like sliding/swishing your turns as most skiers on rockered skis do, then you might feel the same. They are unique among fatties in that they have lots of sidecut and thus are a carver's ski.
The Oracle, a mid fat, maxes out at 175. I understand their philospophy is short fat and stiff though.