To/From Canada or other International destinations, the private carriers are under very strict requirements for Customs. Used personal equipment may still be dutied, new definitely will be. USPS usually avoids these.
USPS maximum girth (circumference) + length can't exceed 108". Private carriers asses Additional Handling when any one side exceeds 60". When shipping by UPS/FX/DHL Air, actual weight may be superseded by what they call "dimensional weight", an arbitrary factor that basically assures that they make a profit.
UPS, FX, DHL all add $5 to charges for items not in a flat-sided box, so bag idea costs extra, as well as frequently jeopardizing safety of bag--they never pay for container damage (that's the purpose of a container, to protect the contents from "normal handling"). Each carrier is capable of loosing or damaging your skis. DHL has poorer service to rural areas. FX Ground is definitely tighter in claims payment than either. Their heritage is RPS, a trucking company, a notorious hard-ass claims environment, and they still haven't absorbed all the FX service ethic.
If I was going to a major event or trip of a lifetime and had to ship, I'd choose FX Air (their technology is the best). If I was selling rock skis to a cheapskate eBayer, ship postal. You should also be aware that anything, when checked as baggage on a passenger plane, has its value limited by F.A.A. and Geneva Convention to something like $100/bag. If you've got high value stuff, whether it's skis or business equipment, you should consider shipping it ahead instead of checking it as a bag.
I like to package un-bindered skis nestled like spoons w/light padding in between, then wrapped in multiple layers of cardboard. With bindings, secure the brakes, face the bases outward and reverse the tips so the bindings are inside and counter positioned. Then you have flat outside surface for load bearing, instead of a binding bulge that will push through the box. Use a genuine ski box recycled from your local shop's dumpster, or two long square boxes inserted into each other, or a carpet tube scrounged from carpet store cut to length, or plastic sewer pipe. DO NOT assume that skis won't get damaged. Bindings get torn off, edges dinged, bases scratched. Ends are particularly vulnerable. Pack for a hostile environment. The length of skis exposes them to lots of torque when made part of a load of hundreds of packages, some weighing up to 150 lbs.