I just flew back from IAH to DEN with a magnum of Champagne in my garment bag. I packed around it, put it in the middle of the bottom between the rails and it got here just fine. I don't know of any/many cargo holds in pax aircraft that are not pressurized. But I could be wrong, my experience with carrying booze of all types in checked luggage has been uniformly uneventful.

Bon Voyage!