diff --git a/pcbnew/pad.cpp b/pcbnew/pad.cpp
index 6ffb39bf3b..222d0f37e3 100644
--- a/pcbnew/pad.cpp
+++ b/pcbnew/pad.cpp
@@ -72,8 +72,9 @@ PAD::PAD( FOOTPRINT* parent ) :
     m_padStack( this )
 {
     VECTOR2I& drill = m_padStack.Drill().size;
-    VECTOR2I& size = m_padStack.Size( PADSTACK::ALL_LAYERS );
-    size.x = size.y = EDA_UNIT_UTILS::Mils2IU( pcbIUScale, 60 ); // Default pad size 60 mils.
+    m_padStack.SetSize( { EDA_UNIT_UTILS::Mils2IU( pcbIUScale, 60 ),
+                          EDA_UNIT_UTILS::Mils2IU( pcbIUScale, 60 ) },
+                        PADSTACK::ALL_LAYERS );
     drill.x = drill.y = EDA_UNIT_UTILS::Mils2IU( pcbIUScale, 30 );       // Default drill size 30 mils.
     m_lengthPadToDie      = 0;
 
diff --git a/pcbnew/pad.h b/pcbnew/pad.h
index 4d4ab33f9a..683f6ae130 100644
--- a/pcbnew/pad.h
+++ b/pcbnew/pad.h
@@ -260,7 +260,7 @@ public:
 
     void SetSize( PCB_LAYER_ID aLayer, const VECTOR2I& aSize )
     {
-        m_padStack.Size( aLayer ) = aSize;
+        m_padStack.SetSize( aSize, aLayer );
         SetDirty();
     }
     const VECTOR2I& GetSize( PCB_LAYER_ID aLayer ) const { return m_padStack.Size( aLayer ); }
@@ -270,10 +270,27 @@ public:
     // in the GUI when the padstack mode is set to anything other than NORMAL, but so that the code
     // compiles, these are set up to work with the front layer (in other words, assume the mode is
     // NORMAL, where F_Cu stores the whole padstack data)
-    void SetSizeX( const int aX ) { if( aX > 0 ) { m_padStack.Size( PADSTACK::ALL_LAYERS ).x = aX; SetDirty(); } }
-    int GetSizeX() const          { return m_padStack.Size( PADSTACK::ALL_LAYERS ).x; }
-    void SetSizeY( const int aY ) { if( aY > 0 ) { m_padStack.Size( PADSTACK::ALL_LAYERS ).y = aY; SetDirty(); } }
-    int GetSizeY() const          { return m_padStack.Size( PADSTACK::ALL_LAYERS ).y; }
+    void SetSizeX( const int aX )
+    {
+        if( aX > 0 )
+        {
+            m_padStack.SetSize( { aX, m_padStack.Size( PADSTACK::ALL_LAYERS ).y }, PADSTACK::ALL_LAYERS );
+            SetDirty();
+        }
+    }
+
+    int GetSizeX() const { return m_padStack.Size( PADSTACK::ALL_LAYERS ).x; }
+
+    void SetSizeY( const int aY )
+    {
+        if( aY > 0 )
+        {
+            m_padStack.SetSize( { m_padStack.Size( PADSTACK::ALL_LAYERS ).x, aY }, PADSTACK::ALL_LAYERS );
+            SetDirty();
+        }
+    }
+
+    int GetSizeY() const { return m_padStack.Size( PADSTACK::ALL_LAYERS ).y; }
 
     void SetDelta( PCB_LAYER_ID aLayer, const VECTOR2I& aSize )
     {
diff --git a/pcbnew/padstack.cpp b/pcbnew/padstack.cpp
index a2a99c16f4..3778c6496d 100644
--- a/pcbnew/padstack.cpp
+++ b/pcbnew/padstack.cpp
@@ -144,7 +144,7 @@ bool PADSTACK::Deserialize( const google::protobuf::Any& aContainer )
     if( padstack.layers_size() == 1 )
     {
         const PadStackLayer& layer = padstack.layers( 0 );
-        Size( ALL_LAYERS ) = kiapi::common::UnpackVector2( layer.size() );
+        SetSize( kiapi::common::UnpackVector2( layer.size() ), ALL_LAYERS );
         SetLayerSet( kiapi::board::UnpackLayerSet( layer.layers() ) );
         SetShape( FromProtoEnum<PAD_SHAPE>( layer.shape() ), F_Cu );
         SetAnchorShape( FromProtoEnum<PAD_SHAPE>( layer.custom_anchor_shape() ), F_Cu );
@@ -836,9 +836,12 @@ void PADSTACK::SetShape( PAD_SHAPE aShape, PCB_LAYER_ID aLayer )
 }
 
 
-VECTOR2I& PADSTACK::Size( PCB_LAYER_ID aLayer )
+void PADSTACK::SetSize( const VECTOR2I& aSize, PCB_LAYER_ID aLayer )
 {
-    return CopperLayer( aLayer ).shape.size;
+    // File formats do not enforce that sizes are always positive, but KiCad requires it
+    VECTOR2I& size = CopperLayer( aLayer ).shape.size;
+    size.x = std::abs( aSize.x );
+    size.y = std::abs( aSize.y );
 }
 
 
diff --git a/pcbnew/padstack.h b/pcbnew/padstack.h
index 02201e1ce2..f3f89655fc 100644
--- a/pcbnew/padstack.h
+++ b/pcbnew/padstack.h
@@ -338,7 +338,8 @@ public:
     PAD_SHAPE Shape( PCB_LAYER_ID aLayer ) const;
     void SetShape( PAD_SHAPE aShape, PCB_LAYER_ID aLayer );
 
-    VECTOR2I& Size( PCB_LAYER_ID aLayer );
+    // Setter rather than direct access to enforce only positive sizes
+    void SetSize( const VECTOR2I& aSize, PCB_LAYER_ID aLayer );
     const VECTOR2I& Size( PCB_LAYER_ID aLayer ) const;
 
     PAD_DRILL_SHAPE DrillShape() const;
diff --git a/pcbnew/pcb_io/altium/altium_pcb.cpp b/pcbnew/pcb_io/altium/altium_pcb.cpp
index 74458dea36..bd579acf30 100644
--- a/pcbnew/pcb_io/altium/altium_pcb.cpp
+++ b/pcbnew/pcb_io/altium/altium_pcb.cpp
@@ -3136,17 +3136,19 @@ void ALTIUM_PCB::ConvertVias6ToFootprintItem( FOOTPRINT* aFootprint, const AVIA6
     else if( aElem.viamode == ALTIUM_PAD_MODE::TOP_MIDDLE_BOTTOM )
     {
         pad->Padstack().SetMode( PADSTACK::MODE::FRONT_INNER_BACK );
-        pad->Padstack().Size( PADSTACK::INNER_LAYERS ) =
-            VECTOR2I( aElem.diameter_by_layer[1], aElem.diameter_by_layer[1] );
+        pad->Padstack().SetSize( VECTOR2I( aElem.diameter_by_layer[1], aElem.diameter_by_layer[1] ),
+                                 PADSTACK::INNER_LAYERS );
     }
     else
     {
         pad->Padstack().SetMode( PADSTACK::MODE::CUSTOM );
+        int altiumIdx = 0;
 
-        for( int ii = 0; ii < 32; ++ii )
+        for( PCB_LAYER_ID layer : LAYER_RANGE( F_Cu, B_Cu, 32 ) )
         {
-            VECTOR2I size( aElem.diameter_by_layer[ii], aElem.diameter_by_layer[ii] );
-            pad->Padstack().Size( static_cast<PCB_LAYER_ID>( F_Cu + ii ) ) = size;
+            pad->Padstack().SetSize( VECTOR2I( aElem.diameter_by_layer[altiumIdx],
+                                               aElem.diameter_by_layer[altiumIdx] ), layer );
+            altiumIdx++;
         }
     }
 
@@ -3388,7 +3390,7 @@ void ALTIUM_PCB::ConvertPads6ToFootprintItemOnCopper( FOOTPRINT* aFootprint, con
         {
             int altLayer = CopperLayerToOrdinal( aLayer );
 
-            ps.Size( aLayer ) = aSize;
+            ps.SetSize( aSize, aLayer );
 
             switch( aShape )
             {
diff --git a/pcbnew/pcb_track.cpp b/pcbnew/pcb_track.cpp
index 98e4c42799..fc694115e9 100644
--- a/pcbnew/pcb_track.cpp
+++ b/pcbnew/pcb_track.cpp
@@ -311,7 +311,7 @@ double PCB_VIA::Similarity( const BOARD_ITEM& aOther ) const
 
 void PCB_VIA::SetWidth( int aWidth )
 {
-    m_padStack.Size( PADSTACK::ALL_LAYERS ) = { aWidth, aWidth };
+    m_padStack.SetSize( { aWidth, aWidth }, PADSTACK::ALL_LAYERS );
 }