We brought our frozen hides and skulls back on the plane, just like they were frozen fish. They went through the long flight from Vancouver to Indianapolis (including layover) just fine. As long as the hides are prepped properly like Firediver said and then frozen really good. We had no problems. I personally wouldn't send my gear ahead, unless I sent it ahead by several weeks as things seem to get loss. I have flown with rifles many times and as long as you have your ammo in another area and are prepared to take the extra few minutes to have it inspected, sealed and locked, we have had no problems. Honeslty we have had more problems with our bows than with guns. Be sure and have your paperwork accurate and ready. Also, your passports.
We have shipped our stuff HOME using UPS, that was easier, because he had bear hides/skulls to deal with at the airport on the way home. On one trip my husband didn't take his bear till last minute, so we left it with the outfitter to freeze and then take to taxidermist. When we finally got the bear pelt home it had slipped a bunch of hair. So our lesson was to try and keep all of our stuff in our possession if at all possible.
Have a great trip, we look forward to reading about it here.