diff --git a/pcbnew/pad.cpp b/pcbnew/pad.cpp
index d50eb76070..46779bd60b 100644
--- a/pcbnew/pad.cpp
+++ b/pcbnew/pad.cpp
@@ -1422,11 +1422,11 @@ void PAD::Flip( const VECTOR2I& aCentre, FLIP_DIRECTION aFlipDirection )
     MIRROR( m_pos, aCentre, aFlipDirection );
 
     m_padStack.ForEachUniqueLayer(
-        [&]( PCB_LAYER_ID aLayer )
-        {
-            MIRROR( m_padStack.Offset( aLayer ), VECTOR2I{ 0, 0 }, aFlipDirection );
-            MIRROR( m_padStack.TrapezoidDeltaSize( aLayer ), VECTOR2I{ 0, 0 }, aFlipDirection );
-        } );
+            [&]( PCB_LAYER_ID aLayer )
+            {
+                MIRROR( m_padStack.Offset( aLayer ), VECTOR2I{ 0, 0 }, aFlipDirection );
+                MIRROR( m_padStack.TrapezoidDeltaSize( aLayer ), VECTOR2I{ 0, 0 }, aFlipDirection );
+            } );
 
     SetFPRelativeOrientation( -GetFPRelativeOrientation() );
 
@@ -1446,28 +1446,25 @@ void PAD::Flip( const VECTOR2I& aCentre, FLIP_DIRECTION aFlipDirection )
                           };
 
     Padstack().ForEachUniqueLayer(
-        [&]( PCB_LAYER_ID aLayer )
-        {
-            if( aFlipDirection == FLIP_DIRECTION::LEFT_RIGHT )
+            [&]( PCB_LAYER_ID aLayer )
             {
-                mirrorBitFlags( m_padStack.ChamferPositions( aLayer ), RECT_CHAMFER_TOP_LEFT,
-                                RECT_CHAMFER_TOP_RIGHT );
-                mirrorBitFlags( m_padStack.ChamferPositions( aLayer ), RECT_CHAMFER_BOTTOM_LEFT,
-                                RECT_CHAMFER_BOTTOM_RIGHT );
-            }
-            else
-            {
-                mirrorBitFlags( m_padStack.ChamferPositions( aLayer ), RECT_CHAMFER_TOP_LEFT,
-                                RECT_CHAMFER_BOTTOM_LEFT );
-                mirrorBitFlags( m_padStack.ChamferPositions( aLayer ), RECT_CHAMFER_TOP_RIGHT,
-                                RECT_CHAMFER_BOTTOM_RIGHT );
-            }
-        } );
+                if( aFlipDirection == FLIP_DIRECTION::LEFT_RIGHT )
+                {
+                    mirrorBitFlags( m_padStack.ChamferPositions( aLayer ), RECT_CHAMFER_TOP_LEFT,
+                                    RECT_CHAMFER_TOP_RIGHT );
+                    mirrorBitFlags( m_padStack.ChamferPositions( aLayer ), RECT_CHAMFER_BOTTOM_LEFT,
+                                    RECT_CHAMFER_BOTTOM_RIGHT );
+                }
+                else
+                {
+                    mirrorBitFlags( m_padStack.ChamferPositions( aLayer ), RECT_CHAMFER_TOP_LEFT,
+                                    RECT_CHAMFER_BOTTOM_LEFT );
+                    mirrorBitFlags( m_padStack.ChamferPositions( aLayer ), RECT_CHAMFER_TOP_RIGHT,
+                                    RECT_CHAMFER_BOTTOM_RIGHT );
+                }
+            } );
 
-    // Flip padstack geometry
-    int copperLayerCount = BoardCopperLayerCount();
-
-    m_padStack.FlipLayers( copperLayerCount );
+    m_padStack.FlipLayers( GetBoard() );
 
     // Flip pads layers after padstack geometry
     LSET flipped;
diff --git a/pcbnew/padstack.cpp b/pcbnew/padstack.cpp
index 150197040c..cb12f5b31d 100644
--- a/pcbnew/padstack.cpp
+++ b/pcbnew/padstack.cpp
@@ -1415,14 +1415,77 @@ bool PADSTACK::HasExplicitDefinitionForLayer( PCB_LAYER_ID aLayer ) const
 
 double PADSTACK::Similarity( const PADSTACK& aOther ) const
 {
-    // TODO: Implement similarity
-    return 0.0;
+    double similarity = 1.0;
+
+    if( m_mode != aOther.m_mode )
+        similarity *= 0.9;
+
+    if( m_layerSet != aOther.m_layerSet )
+        similarity *= 0.9;
+
+    if( m_customName != aOther.m_customName )
+        similarity *= 0.9;
+
+    if( m_orientation != aOther.m_orientation )
+        similarity *= 0.9;
+
+    if( m_frontMaskProps != aOther.m_frontMaskProps )
+        similarity *= 0.9;
+
+    if( m_backMaskProps != aOther.m_backMaskProps )
+        similarity *= 0.9;
+
+    if( m_unconnectedLayerMode != aOther.m_unconnectedLayerMode )
+        similarity *= 0.9;
+
+    if( m_customShapeInZoneMode != aOther.m_customShapeInZoneMode )
+        similarity *= 0.9;
+
+    if( m_drill != aOther.m_drill )
+        similarity *= 0.9;
+
+    if( m_secondaryDrill != aOther.m_secondaryDrill )
+        similarity *= 0.9;
+
+    if( m_tertiaryDrill != aOther.m_tertiaryDrill )
+        similarity *= 0.9;
+
+    if( m_frontPostMachining != aOther.m_frontPostMachining )
+        similarity *= 0.9;
+
+    if( m_backPostMachining != aOther.m_backPostMachining )
+        similarity *= 0.9;
+
+    ForEachUniqueLayer(
+            [&]( PCB_LAYER_ID aLayer )
+            {
+                similarity *= CopperLayer( aLayer ).Similarity( aOther.CopperLayer( aLayer ) );
+            } );
+
+    return similarity;
 }
 
 
-void PADSTACK::FlipLayers( int aLayerCount )
+void PADSTACK::FlipLayers( BOARD* aBoard )
 {
-    // TODO: Implement FlipLayers
+    std::unordered_map<PCB_LAYER_ID, COPPER_LAYER_PROPS> oldCopperProps = m_copperProps;
+    m_copperProps.clear();
+
+    for( const auto& [layer, props] : oldCopperProps )
+        m_copperProps[aBoard->FlipLayer( layer )] = props;
+
+    std::swap( m_frontMaskProps, m_backMaskProps );
+
+    m_drill.start = aBoard->FlipLayer( m_drill.start );
+    m_drill.end = aBoard->FlipLayer( m_drill.end );
+
+    m_secondaryDrill.start = aBoard->FlipLayer( m_secondaryDrill.start );
+    m_secondaryDrill.end = aBoard->FlipLayer( m_secondaryDrill.end );
+
+    m_tertiaryDrill.start = aBoard->FlipLayer( m_tertiaryDrill.start );
+    m_tertiaryDrill.end = aBoard->FlipLayer( m_tertiaryDrill.end );
+
+    std::swap( m_frontPostMachining, m_backPostMachining );
 }
 
 
@@ -1511,6 +1574,35 @@ bool PADSTACK::COPPER_LAYER_PROPS::operator==( const COPPER_LAYER_PROPS& aOther
 }
 
 
+double PADSTACK::COPPER_LAYER_PROPS::Similarity( const PADSTACK::COPPER_LAYER_PROPS& aOther ) const
+{
+    double similarity = 1.0;
+
+    if( shape != aOther.shape )
+        similarity *= 0.5;
+
+    if( zone_connection != aOther.zone_connection )
+        similarity *= 0.9;
+
+    if( thermal_spoke_width != aOther.thermal_spoke_width )
+        similarity *= 0.9;
+
+    if( thermal_spoke_angle != aOther.thermal_spoke_angle )
+        similarity *= 0.9;
+
+    if( thermal_gap != aOther.thermal_gap )
+        similarity *= 0.9;
+
+    if( clearance != aOther.clearance )
+        similarity *= 0.9;
+
+    if( custom_shapes != aOther.custom_shapes )
+        similarity *= 0.5;
+
+    return similarity;
+}
+
+
 #define TEST_OPT( a, b, v )                                           \
         {                                                             \
             if( a.has_value() != b.has_value() )                      \
diff --git a/pcbnew/padstack.h b/pcbnew/padstack.h
index f1374fab4a..8b19c1d6d8 100644
--- a/pcbnew/padstack.h
+++ b/pcbnew/padstack.h
@@ -240,6 +240,8 @@ public:
 
         bool operator==( const COPPER_LAYER_PROPS& aOther ) const;
         int Compare( const COPPER_LAYER_PROPS& aOther ) const;
+
+        double Similarity( const COPPER_LAYER_PROPS& aOther ) const;
     };
 
     ///! The features of a padstack that can vary on outer layers.
@@ -325,7 +327,7 @@ public:
      * Flips the padstack layers in the case that the pad's parent footprint is flipped to the
      * other side of the board.
      */
-    void FlipLayers( int aCopperLayerCount );
+    void FlipLayers( BOARD* aBoard );
 
     PCB_LAYER_ID StartLayer() const;
     PCB_LAYER_ID EndLayer() const;