@swbca I haven't read this whole thread so I apologize if this has been covered -
There is more material than you think before you hit the core, certainly enough to change the ski and make it act completely different. And if you're like me and you sand into the core sometimes, just soak it with epoxy and keep going. Ignore anyone who tells you not to modify your ski. Take it from someone who has been modifying skis for a long time...everyone thinks you're crazy when you do it, that's just part of the deal.
I'll give one warning: almost every ski I've ever modified the bevels on has ended up trash. This is because if I make a change and it's better, I'll inevitably keep sanding to try and make it better-er...until I go to far and it starts to really suck. That's just part of the process though, enjoy!