Is "search + use arch" the right way to derive a form ?

I wanted to add a child task creation form. So I wan't this form to have all fields of default task form, but no header, and action to create the child. So I made a wizard with a osv.Model class with inherit="project.task" and a method returning an action to open a form on a new task with well defined defaults in context. So far, so good. For the form to use, I did want to use all fields from the task form, so first I inherit base form. That was a mistake, as inheriting, in fact modify the base form. My goal was to have yet another form, not modifying existing one. So what I did is to get the arch field from original form using the search+model+use attributes on my field : amr_project.task.add_child_baseproject.taskamr_project.task.add_childproject.task Is that the right way ? Am I missing something ?