I use the REI's XXX duffle to lug my 44" rod tube up to Canada. Although the duffle is 42" long, it is a soft bag and it easily accommodates my 44" tube. I usually put some clothing around the tube and put some REI straps on the outside to keep the bulk down. I have not had any problems with the airlines accepting the bag as regular luggage, although I have to admit that I am always waiting for the front counter people to tell me that it is subject to the excess size charge. But again, I have never been charged the fee and my bags have always made it to my destination.
See the REI bag at:
http://www.rei.com/product/748505
Ron