[Zope] Subfolders within 'Extensions'

Exploring Pyrhon External Methods and wanting to upload a lot of python modules and keep them tidy. For example imaging files into Extensions to do live thmumbnailing and image composition. So far have not been too successful with python scripts importing form the Extensions folder... Any sepcial tips about calling modules from python in External Methods? Are subfolders allowed in 'Extensions' ? Thanks - Jason