Just curious why a Kastle HP ski seems to be so good in powder. For me powder skis have always been about flex (and 2 sheets out titanal are NOT helpful in powder...) and release, which where tip and tail rocker are very helpful (Kastle tails is great in all sorts of snow but may be still too substantial in real powder). You can manage a wid-ish stout ski in real powder if it is short, which could be something that is going on here, but I would always refer a softer longer ski with more rocker for those conditions. I recently had a few days skiing an FX95HP in real powder, and while being passable and even capable, they were way less enjoyable than my softer wider more rocker'y 112RPs in the same type of conditions. On the Kastles It was first time when I felt that I was running out of strength in the middle of a long run. 112RPs would have been almost automatic all the way.
105HP seems to be a very "popular" freeride competition ski (and I totally understand why because its a damp predictable crud blaster that it almost impossible to knock off-course- precisely what you need in a comp ski), but that I would not call a powder ski skill set ...