Replying to If you have access to a drum / surface sander...

build a jig and use it to profile your cores rather than a planer.  Sand abrasion is the most accurate form of material removal, and it puts far less stress on your cores / sidewalls than does blade removal.  This is coming from personal experience, and after having to re-epoxy my sidewalls back on after the planer mutilated them over and over, i decided "what the hell" and tried the surface sander.  I'm now investing in my own.  it's 3000 bucks compared to a 200 dollar planer, but if you're looking to do a lot of skis... soooo nice.  Just thought I'd share, because this was one of the biggest problems i ran into during my building process and the surface sander made it foolproof.

Happy building.