diff --git a/CHANGELOG.md b/CHANGELOG.md
index 170dca4..3b538ab 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,12 @@ Activate / deactivate layer opacity according to prefix
 Activate / deactivate all masks using MA layers
 -->
 
+1.6.2
+
+- changed: Default fileout format changed from `OPEN_EXR` to `OPEN_EXR_MULTILAYER` (a `FILE_FORMAT` env variable can be set to specify nodes format)
+- changed: Default compression changed from `ZIP` to `PIZ`
+- changed: Rename/renumber function consider OPEN_EXR_MULTILAYER to affect `layer_slots` instead of `file_slots`
+
 1.6.1
 
 - fixed: preview output for Blender 4.0+
diff --git a/OP_check_scene.py b/OP_check_scene.py
index ea8abaf..a30d011 100644
--- a/OP_check_scene.py
+++ b/OP_check_scene.py
@@ -64,8 +64,6 @@ def check_file_output_numbering(reports=None):
             continue
         file_outs += [n for n in S.node_tree.nodes if n.type == 'OUTPUT_FILE']
 
-    used=False
-
     if not file_outs:
         reports.append('No file output nodes found')
         return reports
@@ -74,11 +72,12 @@ def check_file_output_numbering(reports=None):
         if not prenum.match(fo.base_path.split('/')[-1]):
             reports.append(f'No object numbering : node {fo.name}')
         pct = 0
-        for fs in fo.file_slots:
+        slots = fo.layer_slots if fo.format.file_format == 'OPEN_EXR_MULTILAYER' else fo.file_slots
+        for fs in slots:
             if not prenum.match(fs.path.split('/')[0]):
                 pct += 1
         if pct:
-            reports.append(f'{pct}/{len(fo.file_slots)} slots not numbered: node {fo.name}')
+            reports.append(f'{pct}/{len(slots)} slots not numbered: node {fo.name}')
 
     return reports
 class GPEXP_OT_check_render_scene(bpy.types.Operator):
diff --git a/__init__.py b/__init__.py
index 5711654..adb81af 100644
--- a/__init__.py
+++ b/__init__.py
@@ -2,7 +2,7 @@ bl_info = {
     "name": "GP Render",
     "description": "Organise export of gp layers through compositor output",
     "author": "Samuel Bernou",
-    "version": (1, 6, 1),
+    "version": (1, 6, 2),
     "blender": (3, 0, 0),
     "location": "View3D",
     "warning": "",
diff --git a/fn.py b/fn.py
index 9131848..cdea6ec 100644
--- a/fn.py
+++ b/fn.py
@@ -150,12 +150,15 @@ def copy_settings(obj_a, obj_b):
             pass
 
 def set_file_output_format(fo):
-    fo.format.file_format = 'OPEN_EXR'
+    # FIXME for now default fallback to multilayer
+    env_file_format = os.environ.get('FILE_FORMAT')
+    fo.format.file_format = env_file_format if env_file_format else 'OPEN_EXR_MULTILAYER'
+    # fo.format.file_format = 'OPEN_EXR' # 'OPEN_EXR_MULTILAYER'
     fo.format.color_mode = 'RGBA'
     fo.format.color_depth = '16'
-    fo.format.exr_codec = 'ZIP'
-    # fo.format.exr_codec = 'RLE'
+    fo.format.exr_codec = 'PIZ' # 'ZIP', 'RLE'
 
+    ## PNG format
     # fo.format.file_format = 'PNG'
     # fo.format.color_mode = 'RGBA'
     # fo.format.color_depth = '8'
@@ -898,21 +901,26 @@ def get_numbered_output(out, slot_name):
 
 
 def add_fileslot_number(fs, number):
-    elems = fs.path.split('/')
+    field_attr = 'name' if hasattr(fs, 'name') else 'path'
+
+    elems = getattr(fs, field_attr).split('/')
     for i, e in enumerate(elems):
         if re.match(r'^\d{3}_', e):
             elems[i] = re.sub(r'^(\d{3})', lambda x: str(number).zfill(3), e)
         else:
             elems[i] = f'{str(number).zfill(3)}_{e}'
     new = '/'.join(elems)
-    fs.path = new
+
+    setattr(fs, field_attr, new)
     return new
 
 def renumber(fo, offset=10):
     '''Force renumber all the slots with a 3'''
+
     if fo.type != 'OUTPUT_FILE': return
     ct = 10 # start at 10
-    for fs in fo.file_slots:
+    slots = fo.layer_slots if fo.format.file_format == 'OPEN_EXR_MULTILAYER' else fo.file_slots 
+    for fs in slots:
         add_fileslot_number(fs, ct)
         ct += offset
 
@@ -921,7 +929,11 @@ def get_num(string) -> int:
     return leading number or None
     '''
     if not isinstance(string, str):
-        string = string.path
+        if hasattr(string, 'path'):
+            string = string.path
+        else:
+            string = string.name
+
     num = re.search(r'^(\d{3})_', string)
     if num:
         return int(num.group(1))
@@ -930,13 +942,21 @@ def delete_numbering(fo): # padding=3
     '''Delete prefix numbering on all slots on passed file output'''
 
     if fo.type != 'OUTPUT_FILE': return
-    for fs in fo.file_slots:
-        elems = fs.path.split('/')
+
+    if fo.format.file_format == 'OPEN_EXR_MULTILAYER':
+        slots = fo.layer_slots
+        field_attr = 'name'
+    else:
+        slots = fo.file_slots
+        field_attr = 'path'
+
+    for fs in slots:
+        elems = getattr(fs, field_attr).split('/')
         for i, e in enumerate(elems):
             elems[i] = re.sub(r'^\d{3}_', '', e)
 
         new = '/'.join(elems)
-        fs.path = new
+        setattr(fs, field_attr, new)
 
 def reverse_fileout_inputs(fo):
     count = len(fo.inputs)
@@ -954,7 +974,7 @@ def renumber_keep_existing(fo, offset=10, invert=True):
     if invert:
         reverse_fileout_inputs(fo)
 
-    fsl = fo.file_slots
+    fsl = fo.layer_slots if fo.format.file_format == 'OPEN_EXR_MULTILAYER' else fo.file_slots 
 
     last_idx = len(fsl) - 1
     prev = None