Juraj: The default bundles doc does not match anything I see in the admin UI. It begins with, "If you are adding a new product or editing an existing one (on the General tab), you need to select Bundle as the value of the product's Representing property." But I sure don't see anything referring to the Representing property, or to bundles in any way, on that tab (or any of the others).
Dmitry: Thanks for the pointer. Custom coding was what I was hoping to avoid, but sometimes it's not avoidable, I guess