I have had success using 304 sst plate 2" x 6" x.035" with .090 spacing
+nnnn-nnnn+nnnn-nnnn+. I have had very good hho production from using 304sst allthread as positive inside of 3/4" 304 sst tubing as the negative. The high current however brings out a large amount of rust from the alltread. I plan on upgrading to 316 sst 3/8" allthread for my next experiments.