I’m trying to add Italics to my Uprights and intuitively added two more Masters into the same glyphs file (screenshots). I made a test-Italic character afterwards but the Instance preview goes wrong. It seems to interpolate between Light-Upright to Light-Italic (I end up at about 6°), instead of Light-Italic to Bold-Italic.
I couldn’t find a tutorial about a Upright-MM-Italic workflow. Is it perhaps completely wrong to keep Upright and Italics in the same file? I thought I had seen a screenshot like that somewhere …