What is the best way to pack an Ibex that will be in checked luggage for the flight home?

duffle bags of some type should work.you could tape the horns together with duct tape.

Make sure the cape is DRY. Mine was almost held up by USFWS at customs but my pleading worked. IMO, it was dry but they didn't think so.

In addition to what the others have said, make sure you have your CITES export paperwork in hand before leaving with your trophy. The rules changed in 2014 when ibex were listed as an appendix 3 animal and the vet certificates and cites export permits must be in hand before departing with your trophies. Otherwise they can be confiscated by usfws.

Thanks