In reply to Creating a Harmonious Bold:
Old Nick wrote: "If your design has an overall even weight/balance to the strokes, then emboldening is a fairly straightforward matter. However, if your design is medium to high contrast, the process gets trickier."
Funny, I would have said the exact opposite. Though it's a bigger problem in really heavy weights, like a black or an ultra.
What you do with the sidebearings depends on what you do with the distribution of the added weight on the x-axis. Generally speaking, the smaller the internal space, the smaller the sidebearings.