diff --git a/pm2d/line_matcher.py b/pm2d/line_matcher.py
index 87c108f..15967bd 100644
--- a/pm2d/line_matcher.py
+++ b/pm2d/line_matcher.py
@@ -1305,8 +1305,9 @@ class LineShapeMatcher:
         if t is None:
             return 1.0
         h, w = t.shape
-        cx_t = (w - 1) / 2.0
-        cy_t = (h - 1) / 2.0
+        # Coerente con training (center = diag / 2.0, no -1)
+        cx_t = w / 2.0
+        cy_t = h / 2.0
 
         # Bounding box del template ruotato/scalato attorno a (cx, cy)
         diag = int(np.ceil(np.hypot(w, h) * scale)) + 8
diff --git a/pm2d/web/server.py b/pm2d/web/server.py
index 8fdaf68..f1d58fb 100644
--- a/pm2d/web/server.py
+++ b/pm2d/web/server.py
@@ -168,7 +168,10 @@ def _draw_matches(scene: np.ndarray, matches: list[Match],
         if template_gray is not None and matcher is not None:
             t = template_gray
             th, tw = t.shape
-            cx_t = (tw - 1) / 2.0; cy_t = (th - 1) / 2.0
+            # Centro template coerente col training: in train si usa
+            # `center = (diag / 2.0, diag / 2.0)` (no -1). Usare (tw-1)/2
+            # introduceva uno shift di 0.5px per template di lato pari.
+            cx_t = tw / 2.0; cy_t = th / 2.0
             M = cv2.getRotationMatrix2D((cx_t, cy_t), m.angle_deg, m.scale)
             M[0, 2] += m.cx - cx_t
             M[1, 2] += m.cy - cy_t
@@ -181,10 +184,11 @@ def _draw_matches(scene: np.ndarray, matches: list[Match],
             warped_mask = cv2.warpAffine(
                 mask_src, M, (W_scene, H_scene),
                 flags=cv2.INTER_NEAREST, borderValue=0)
-            # Erode di spread_radius per scartare la fascia di transizione
-            # bordo che produce gradient spurio
-            er_k = max(3, 2 * matcher.spread_radius + 1)
-            kernel_er = np.ones((er_k, er_k), np.uint8)
+            # Erode minimo (3x3) per togliere SOLO artefatti border-padding
+            # (~1px di bordo nero da warpAffine borderValue=0). Erode piu'
+            # grande spostava visualmente l'edge verso l'interno e creava
+            # apparente "traslazione fissa" rispetto al bordo del pezzo.
+            kernel_er = np.ones((3, 3), np.uint8)
             warped_mask = cv2.erode(warped_mask, kernel_er)
             mag, _ = matcher._gradient(warped_gray)
             if matcher.weak_grad < matcher.strong_grad: