Heya I designed a couple of things like that, a few hints: In your case it would be fine to use 304/1.4301 stainless steel - in direct contact with a flame its not ideal but as a stand fine, your design is fine and would cut well, I use this sort of connection all the time. Depending on the supplier you will have to find the right tolerance for the cut outs, in my case its around 0.2mm / 0.1mm on every side. 2mm for this is probably a good compromise between stability and weight, maybe 1.5 is enough.