has anyone used stainless steel wire? i'd like to use it on a couple of my stitches.
Yes, not a big deal. Be aware that SS wire is stronger than copper wire, so when you twist SS wire stitches, be careful that you don't twist so tight that you pull the stitches through the ply. Keep your stitch holes at least the recommended distance from joining edges to help prevent tear outs.
And yeah, smaller SS wire might only be as strong as 18 gauge copper, but it's much thinner, so it'll rip through ply easier than the copper. Good luck.