How does window size affect the design?

Smaller windows don't require as much structural planning. The design is more compact, the glass cuts are more compact, the lead is more compact, it's almost supporting itself. But when you scale up to a larger window, there are going to be more open areas with large pieces of glass and longer stretches of lead holding things up. That creates more weak points and more areas you need to be cautious about.

For larger windows, I always start with the structure first. Think of a modern window that's just a grid of squares. You start with that kind of structural framework and then build the design around it. For smaller windows, you can be more lenient. You still want to keep structure in mind, but it's not as critical as it would be with something larger.