After a whole series of gluing the bits and pieces together with epoxy glue, then adding fillets - again with the epoxy glue, we were ready to paint the whole pattern to make sure that we had a relatively flat surface with no indentations that would tear out the sand when we made the mold. Here's some shots of the pattern compared to the original bronze striker plate. This is a front-end view.
Voila - a nice clean mold.
We're going to do it all over again next Saturday only this time we'll add some sprues, gates and risers as I think I'm going to have to be the mold-maker on this project. If I had a foundry, I could even be the foundryman.
PS - Many thanx to Jim L. for his photography expertise.