The more I look at this part the more places I see where loose sand could get caught in one of the small ridges if I cast it normally (lying flat). The small sections (where the holes are) are give or take 6mm wide and 9.5mm deep, or 1/4" x 3/8” in the old money so I’ve been thinking about doing it vertically. Something like this? My thinking is that any loose sand would/could be carried out the top and the entire mold would basically become a vent. Oh ya . . it’s going to be aluminum. Any thoughts?