Two approaches come to mind:
- In your stencil master, draw only the cutouts (use the eye icon in the layers palette to show the other master’s outlines in a sort of preview). Then use a script upon export to combine the two masters together. You need to pay attention that all paths in your stencil master need to be set to mask, or be reversed. There’s a forum post here quite recently that includes the script to combine masters: Export different masters into one export - #8 by JonasG
- Use the first master’s outlines as a component in the stencil master. This is only achievable by script, but you can set the component’s master ID to point to the first master. So, add a GSComponent with the glyph’s name as the component name, and use
GSComponent.setComponetMasterId_()to set its master ID to the first master. Then draw on top of that component.
Be aware I haven’t actually tested these approaches with your exact scenario, but they should work.