John, Yes stainless works better as it doesn't transfer heat well. Any lead landing on the plate immediately hardens, does not stick and just get brushed off.
What I did was take a short length of round rod and center drill it to the size of the existing RCBS downrod. This would slide on the 90 degree bend of the existing rod. I then milled three flat spots the length of the rod then drilled and tapped 4 - 1/4"x28 holes in the rod so two were on the bottom in the flat spot and two on the side. I then centered and welded the rod to the stainless plate with a flat to the plate. I used 4 set screws then just slide the plate on the downrod and tighten the set screws. It would have been less work if I had a piece of square stock which I didn't have so I used the round stock I had on hand. I think the second photo shows it pretty well.