I tried stainless hard oil lines. They cracked, Twice.

 

I would expect that in a high vibration area, a stainless tube without a bellows or rubber section, would break.

 

It is interesting, I thought it would work. My 323 GTX came with a factory hard line on the pressure side and it doesn't break. The 323GTR motor is the same but has a rubber mount point about mid span. The one I made for my Miata cracked the tube once at the flare tube nut going into the turbo and once at the banjo that I silver brazed on after I made it again.

The Teflon braided line with fire sleeve insulation around it has been trouble free.