A couple of us on facebook were mourning the loss of the information on BB about sizing Amal gas injectors for use in forges. Tim, have you got any of the information you posted from there archived that could be reposted here ?
Yours posts were a goldmine of information on this subject
Im thinking of building a slightly bigger than a 13kg gas bottle forge, wool lined, with cast refractory inner shell, and Josh is planning a similar build. I think Will Catchy built something along the lines of what we are thinking about.