this is the program ive been using in my design process. if you need help understanding how to use it pm me. its designed for snowboards but you can do skis with it too. secondly check out skibuilders.com if you have not already.
generally for a park ski companies go with a straighter dimension. such as 117-90-105 for me ill be going around 130-85-115.
it all comes down to what you want out of the ski, more park= less shape, more carve=more shape