diff --git a/planetstack/core/admin.py b/planetstack/core/admin.py
index 1952890..34a77c0 100644
--- a/planetstack/core/admin.py
+++ b/planetstack/core/admin.py
@@ -738,6 +738,9 @@
         cleaned_data = super(SliceForm, self).clean()
         name = cleaned_data.get('name')
         site = cleaned_data.get('site')
+        slice_id = self.instance.id
+        if not site and slice_id:
+            site = Slice.objects.get(id=slice_id).site
         if (not isinstance(site,Site)):
             # previous code indicates 'site' could be a site_id and not a site?
             site = Slice.objects.get(id=site.id)
@@ -781,6 +784,18 @@
             tabs.append( ('admin-only', 'Admin-Only') )
 
         return tabs
+    
+    def add_view(self, request, form_url='', extra_context=None):
+        # revert to default read-only fields
+        self.readonly_fields = ('backend_status_text',)
+        return super(SliceAdmin, self).add_view(request, form_url, extra_context=extra_context)
+
+    def change_view(self, request, object_id, form_url='', extra_context=None):
+        print object_id
+        # cannot change the site of an existing slice so make the site field read only
+        if object_id:
+            self.readonly_fields = ('backend_status_text','site')
+        return super(SliceAdmin, self).change_view(request, object_id, form_url)
 
     def render_change_form(self, request, context, add=False, change=False, form_url='', obj=None):
         deployment_nodes = []
diff --git a/planetstack/core/models/slice.py b/planetstack/core/models/slice.py
index 7915d42..7412fe2 100644
--- a/planetstack/core/models/slice.py
+++ b/planetstack/core/models/slice.py
@@ -87,6 +87,13 @@
             qs = Slice.objects.filter(id__in=slice_ids)
         return qs
 
+    def delete(self, *args, **kwds):
+        # delete networks associated with this slice
+        from core.models.network import Network
+        nets = Network.objects.filter(slices=self)
+        nets.delete() 
+        super(SliceAdmin, self).delete(*args, **kwds) 
+
 class SliceRole(PlCoreBase):
     ROLE_CHOICES = (('admin','Admin'),('default','Default'))