I'm not a trained steam locomotive designer. Reckon I could make myself look pretty stupid by attempting too much in the way of second guessing those who were. But I'm sure you're right about factoring it into design decisions. Consider, for example, if you chamfer the top corners of the axle boxes then haven't you also reduced the bearing surfaces? I'm sure I could easily get lost in a maze of design factors I don't understand if I carried on though. Its become pretty clear to me while I've been writing a book on GWR locomotive classes that for, well, the entire life of the steam locomotive really, many of the designers were spending their time attempting to reconcile competing priorities at the limits of the materials and budgets available to them. I don't think locomotive design was ever easy.