First I would not worry about them skimming off some meat and I think your a little paraniod.
If their pro's you should have no problem. I would go to the country market as an elk is just a big deer to a butcher.
If you want to pull the straps yourself it's easist to skin the animal,run a sharp knife along both sides of the spine top to bottom,then follow up running your knife along the ribs. This will give you 2 long strips of some very tasty meat.
As far as the Ivory I use a big heavy duty knife and digem out.
Good Luck