A bass sax is quite heavy, so unless you want to carry all that weight around your neck, you might want to consider a stand or a harness.

Paul Coats built a stand that I could bring home and attach to an old office chair wheel base. We didn't quite get the measurements right when we measured the diameter of the hole in the chair base, the tubing was slightly too big. After grinding the nylon fitting in the base, I finally managed to get the aluminum tubing to fit into the hole. It fits so well, that I doubt it will ever come apart!

The idea is to have it fit loosely into the opening so you can use cotter pins to adjust the height.

Luckily for me, the stand puts the mouthpiece of the horn at the perfect height for someone 5'9" tall--just my height! I can play my horn while standing, and not have to carry any of the weight.