I've learned a lot by lurking here, but I haven't managed to find the answer to this question by either searching here or consulting Brother Google, so here's a first post.
Do you coordinate the sidebearings of your various masters in a variable font, and if so, how? Would it work to, say, make the sb of Extrabold always some percentage of Light and then tune as necessary? I would have thought to, but when I tried to figure out what Source Serif was doing, I couldn't spot any consistent relationship.
Or is this important at all? Can you get away with doing each master separately and trusting the renderer to come up with appropriate intermediate values? Or is there some more complex formula that I haven't been able to deduce?
Grateful for advice, or for references to discussions here or elsewhere.