I'd be concerned with the hardness of stainless, or brass, over copper. I believe they used soft copper tube because it will conform to the bore when peened easily. You might want to test the stainless before you commit to putting it in the block.
This is only .028 thick so I should be ok peening it with my old Direct Connection tool. I worked with and ran a lot of Stainless grease lines during my 33 years as a Millwright in a steel mill. We shall know very soon if this works and it should help a lot of guys out facing the same issue.
