diff --git a/stimela/cargo/base/aimfast/Dockerfile b/stimela/cargo/base/aimfast/Dockerfile
index 004698bb9..7d0ff53b9 100644
--- a/stimela/cargo/base/aimfast/Dockerfile
+++ b/stimela/cargo/base/aimfast/Dockerfile
@@ -3,4 +3,4 @@ RUN docker-apt-install python3-pip \
                        python3-numpy
 
 RUN pip3 install --upgrade numpy
-RUN pip3 install aimfast==1.0rc3
+RUN pip3 install aimfast==1.0rc11
diff --git a/stimela/cargo/cab/aimfast/parameters.json b/stimela/cargo/cab/aimfast/parameters.json
index a722579d0..01d25fc75 100644
--- a/stimela/cargo/cab/aimfast/parameters.json
+++ b/stimela/cargo/cab/aimfast/parameters.json
@@ -75,21 +75,21 @@
             "dtype": "int"
         }, 
         {
-            "info": "Two tigger model (text/lsm.html) files to compare", 
-            "delimiter": " ", 
-            "name": "compare-models", 
-            "io": "output", 
-            "default": null, 
-            "dtype": "list:file", 
+            "info": "Tigger model (text/lsm.html) files to compare",
+            "delimiter": " ",
+            "name": "compare-models",
+            "io": "output",
+            "default": null,
+            "dtype": "list:file",
             "required": false
         }, 
         {
-            "info": "Two residual (fits) files to compare. e.g: ['res1.fits:res2.fits']", 
-            "delimiter": " ", 
-            "name": "compare-residuals", 
-            "io": "output", 
-            "default": null, 
-            "dtype": "list:file", 
+            "info": "Residual (fits) files to compare. e.g: ['res1.fits', 'res2.fits']",
+            "delimiter": " ",
+            "name": "compare-residuals",
+            "io": "output",
+            "default": null,
+            "dtype": "list:file",
             "required": false
         }, 
         {
@@ -170,6 +170,14 @@
             "required": false,
             "name": "fov-factor",
             "dtype": "float"
+        },
+        {
+            "info": "aimfast fidelity results file (JSON format)",
+            "default": null,
+            "required": false,
+            "name": "fidelity-results",
+            "io": "output",
+            "dtype": "file"
         }
     ]
 }
diff --git a/stimela/cargo/cab/aimfast/src/run.py b/stimela/cargo/cab/aimfast/src/run.py
index 409e0c0c7..4a95c2c73 100644
--- a/stimela/cargo/cab/aimfast/src/run.py
+++ b/stimela/cargo/cab/aimfast/src/run.py
@@ -26,9 +26,15 @@
     elif value is False:
         continue
 
-    if type(value) is list:
-        args += ['{0}{1} {2}'.format(cab['prefix'], name,
-                                     " ".join([val.replace(':output', '') for val in value]))]
+    if 'compare' in name:
+        compare = []
+        for i, val in enumerate(value):
+            compare.append(val)
+            # Compare models/images in pairs
+            if i%2:
+                args += ['{0}{1} {2}'.format(cab['prefix'],
+                                            name, " ".join(compare))]
+                compare = []
     else:
         args += ['{0}{1} {2}'.format(cab['prefix'], name, value)]