diff --git a/nhf/touhou/houjuu_nue/joints.py b/nhf/touhou/houjuu_nue/joints.py
index 04df3f9..c368d60 100644
--- a/nhf/touhou/houjuu_nue/joints.py
+++ b/nhf/touhou/houjuu_nue/joints.py
@@ -95,7 +95,7 @@ class RootJoint(Model):
 
     child_height: float = 60.0
     child_width: float = 50.0
-    child_mount_thickness: float = 25.4 / 8
+    child_mount_thickness: float = 25.4 / 4
 
     def corner_pos(self) -> list[tuple[int, int]]:
         """
@@ -888,6 +888,10 @@ class ElbowJoint(Model):
     def total_thickness(self):
         return self.disk_joint.total_thickness
 
+    @property
+    def motion_span(self) -> float:
+        return self.disk_joint.movement_angle
+
     def parent_arm_loc(self) -> Cq.Location:
         """
         2d Location of the centre of the arm surface on the parent side, assuming
diff --git a/nhf/touhou/houjuu_nue/wing.py b/nhf/touhou/houjuu_nue/wing.py
index 6d9780b..27c4c6e 100644
--- a/nhf/touhou/houjuu_nue/wing.py
+++ b/nhf/touhou/houjuu_nue/wing.py
@@ -24,7 +24,9 @@ class WingProfile(Model):
     root_joint: RootJoint = field(default_factory=lambda: RootJoint())
 
     panel_thickness: float = 25.4 / 16
-    spacer_thickness: float = 25.4 / 8
+    # 1/4" acrylic for the spacer. Anything thinner would threathen structural
+    # strength
+    spacer_thickness: float = 25.4 / 4
 
     shoulder_joint: ShoulderJoint = field(default_factory=lambda: ShoulderJoint(
     ))
@@ -325,9 +327,52 @@ class WingProfile(Model):
     ### s1, s2, s3 ###
     def profile(self) -> Cq.Sketch:
         """
-        Generates profile from shoulder and above
+        Generates profile from shoulder and above. Subclass should implement
         """
 
+    def _elbow_joint_retract_cut_polygon(self, loc: Cq.Location) -> Cq.Sketch:
+        """
+        Creates a cutting polygon for removing the contraction part of a joint
+        """
+        theta = math.radians(self.elbow_joint.motion_span)
+        h = self.elbow_height
+        dx = h * math.tan(theta / 2)
+        dy = h
+        sign = -1 if self.flip else 1
+        points = [
+            (0, 0),
+            (dx, sign * dy),
+            (-dx, sign * dy),
+        ]
+        return (
+            Cq.Sketch()
+            .polygon([
+                (loc * Cq.Location.from2d(*p)).to2d_pos()
+                for p in points
+            ])
+        )
+    def _wrist_joint_retract_cut_polygon(self, loc: Cq.Location) -> Cq.Sketch:
+        """
+        Creates a cutting polygon for removing the contraction part of a joint
+        """
+        theta = math.radians(self.wrist_joint.motion_span)
+        dx = self.wrist_height * math.tan(theta)
+        dy = self.wrist_height
+        sign = -1 if self.flip else 1
+        points = [
+            (0, 0),
+            (0, -sign * dy),
+            (-dx, -sign * dy),
+        ]
+        return (
+            Cq.Sketch()
+            .polygon([
+                (loc * Cq.Location.from2d(*p)).to2d_pos()
+                for p in points
+            ])
+        )
+
+
     def _assembly_insert_spacer(
             self,
             a: Cq.Assembly,
@@ -374,8 +419,7 @@ class WingProfile(Model):
             self,
             joint: ElbowJoint,
             segment_thickness: float,
-            dx: float,
-            bot=False) -> MountingBox:
+            dx: float) -> MountingBox:
         length = joint.lip_length / 2 - dx
         holes = [
             Hole(x - dx)
@@ -398,6 +442,9 @@ class WingProfile(Model):
             self.profile()
             .reset()
             .polygon(self._mask_elbow(), mode='i')
+            .reset()
+            .push([self.elbow_axle_loc])
+            .each(self._elbow_joint_retract_cut_polygon, mode='s')
         )
         return profile
     def surface_s1(self, front: bool = True) -> Cq.Workplane:
@@ -471,6 +518,12 @@ class WingProfile(Model):
             .polygon(self._mask_elbow(), mode='s')
             .reset()
             .polygon(self._mask_wrist(), mode='i')
+            .reset()
+            .push([self.elbow_axle_loc])
+            .each(self._elbow_joint_retract_cut_polygon, mode='s')
+            .reset()
+            .push([self.wrist_axle_loc])
+            .each(self._wrist_joint_retract_cut_polygon, mode='s')
         )
         return profile
     def surface_s2(self, front: bool = True) -> Cq.Workplane:
@@ -638,7 +691,7 @@ class WingProfile(Model):
                 .constrain("s1/shoulder_bot?conn1", f"shoulder/child/lip_{tag_bot}?conn1", "Plane")
             )
         if "elbow" in parts:
-            angle = self.elbow_joint.disk_joint.movement_angle * elbow_wrist_deflection
+            angle = self.elbow_joint.motion_span * elbow_wrist_deflection
             result.add(self.elbow_joint.assembly(angle=angle), name="elbow")
         if "s1" in parts and "elbow" in parts:
             (
@@ -659,7 +712,7 @@ class WingProfile(Model):
                 .constrain("s2/elbow_bot?conn1", f"elbow/child/lip?conn_{tag_bot}1", "Plane")
             )
         if "wrist" in parts:
-            angle = self.wrist_joint.disk_joint.movement_angle * elbow_wrist_deflection
+            angle = self.wrist_joint.motion_span * elbow_wrist_deflection
             result.add(self.wrist_joint.assembly(angle=angle), name="wrist")
         if "s2" in parts and "wrist" in parts:
             # Mounted backwards to bend in other direction