Sorry for the scribble. I think that you can tell what’s going on. If you have free lance machinist you could have this done in aluminum. You could do the low temp silicone compound then.
Drilling the holes I double everything up so that all the holes and dowels line up. I do the two sizes of sides - 1” and 1 1/2” so that I can pour
one half, then pour the second half on top. I’ll
send a couple of pictures of my hard urethane molds separately. Feel free to ask me any questions.