diff --git a/libs/ardour/ardour/slice.h b/libs/ardour/ardour/slice.h
index d5b05e41f4..8c6163df0d 100644
--- a/libs/ardour/ardour/slice.h
+++ b/libs/ardour/ardour/slice.h
@@ -18,7 +18,7 @@ namespace Properties {
 	LIBARDOUR_API extern PBD::PropertyDescriptor<timecnt_t>         length;
 }
 
-class LIBARDOUR_API Slice : virtual public PBD::Stateful
+class LIBARDOUR_API Slice
 {
   public:
   	Slice (Temporal::timepos_t const &, Temporal::timecnt_t const &);
@@ -33,6 +33,10 @@ class LIBARDOUR_API Slice : virtual public PBD::Stateful
 	timepos_t end()        const;
 	timepos_t nt_last()    const { return end().decrement(); }
 
+	virtual void set_start (timepos_t const & s) { _start = s; }
+	virtual void set_position (timepos_t const & p);
+	virtual void set_length (timecnt_t const &);
+
 	/* these two are valid ONLY during a StateChanged signal handler */
 
 	timepos_t last_position () const { return _last_length.position(); }
@@ -112,9 +116,6 @@ class LIBARDOUR_API Slice : virtual public PBD::Stateful
 	virtual void set_length_internal (timecnt_t const &);
 	virtual void set_start_internal (timepos_t const &);
 	virtual void set_position_internal (timepos_t const &);
-
-  private:
-  	void register_properties ();
 };
 
 } /* namespace */
diff --git a/libs/ardour/region.cc b/libs/ardour/region.cc
index 0dd0e28846..03947eb828 100644
--- a/libs/ardour/region.cc
+++ b/libs/ardour/region.cc
@@ -195,6 +195,13 @@ Region::register_properties ()
 {
 	_xml_node_name = X_("Region");
 
+	/* anything derived from Slice must remember to add these properties to
+	 * Stateful's list, since Slice does not do this itself.
+	 */
+
+	add_property (_start);
+	add_property (_length);
+
 	add_property (_muted);
 	add_property (_opaque);
 	add_property (_locked);
diff --git a/libs/ardour/slice.cc b/libs/ardour/slice.cc
index 55d5a6d20f..7bafebbfdd 100644
--- a/libs/ardour/slice.cc
+++ b/libs/ardour/slice.cc
@@ -8,7 +8,6 @@ Slice::Slice (timepos_t const & s, timecnt_t const & l)
 	, _length (Properties::length, l)
 	, _last_length (l)
 {
-	register_properties ();
 }
 
 Slice::Slice (Slice const & other)
@@ -19,10 +18,17 @@ Slice::Slice (Slice const & other)
 }
 
 void
-Slice::register_properties ()
+Slice::set_position (timepos_t const & pos)
 {
-	add_property (_start);
-	add_property (_length);
+	_length = timecnt_t (_length.val().distance(), pos);
+	_last_length = _length;
+}
+
+void
+Slice::set_length (timecnt_t const & len)
+{
+	_last_length = _length;
+	_length = timecnt_t (len.distance(), _length.val().position());
 }
 
 timepos_t