I have found putting some grease or oil on the back side of the flare and on the threads of the nuts helps, stainless steel will be worse for galling up. A steel nut on stainless tubing will bad, but a stainless nut on stainless tube will really be bad. I have worked on stainless steel lines on Compressed Natural Gas buses for years, and without some type of lubricant on the threads, you about guarantied to galled them together.
