Playing around with conventions and have discovered this.
<Conventions>
<handlersLocation>_controllers</handlersLocation>
<pluginsLocation>_plugins</pluginsLocation>
<layoutsLocation>_layouts</layoutsLocation>
<viewsLocation>_views</viewsLocation>
</Conventions>
Works, but the following will only error when it tries to run the event/view/ or whatever.
<Conventions>
<handlersLocation>test/_controllers</handlersLocation>
<pluginsLocation>test/_plugins</pluginsLocation>
<layoutsLocation>test/_layouts</layoutsLocation>
<viewsLocation>test/_views</viewsLocation>
</Conventions>
Create the directory and it will flow through, but as indicated it won't run the event.