You need to set a very simple redirect, from a specific location on your IIS web site or application, to a new URL? Then place this very simple default.aspx page at that location; in most of the case...
Updated Aug 23, 2019
Version 1.0
Blog Post
True, Default.aspx is not the most performant solution. But it is very likely that a "default.aspx" entry exists in the Default Documents configuration. Your solution with Global.asax looks nice; I'm not sure if you can put a global.asax on any folder level in an app.