diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3397989..257c4e9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -59,6 +59,13 @@ enable_testing()
               )
              set_tests_properties(test_horus_binary PROPERTIES PASS_REGULAR_EXPRESSION "1C9A9545")
 
+     add_test(NAME test_horus_binary_v2
+             COMMAND sh -c "cd ${CMAKE_CURRENT_BINARY_DIR}/src;
+                            sox -t raw -r 8000 -e signed-integer -b 16 -c 1 ${CMAKE_CURRENT_SOURCE_DIR}/samples/horus_v2_100bd.raw -r 48000 -t raw - | 
+                            ./horus_demod -m binary - -"
+              )
+             set_tests_properties(test_horus_binary_v2 PROPERTIES PASS_REGULAR_EXPRESSION "0102030405060708091DBB")
+
      add_test(NAME test_horus_rtty_7n1
              COMMAND sh -c "cd ${CMAKE_CURRENT_BINARY_DIR}/src;
                             sox ${CMAKE_CURRENT_SOURCE_DIR}/samples/rtty_7n1.wav -r 48000 -t raw - |
diff --git a/custom_field_list.json b/custom_field_list.json
index 882ef3d..098dfb7 100644
--- a/custom_field_list.json
+++ b/custom_field_list.json
@@ -29,7 +29,7 @@
         ["test_field 6", "none"],
         ["test_field 7", "none"],
         ["test_field 8", "none"],
-        ["test_field 9", "none"],
+        ["test_field 9", "none"]
     ]
 }
 }
\ No newline at end of file
diff --git a/horusdemodlib/__init__.py b/horusdemodlib/__init__.py
index f4bd716..3ced358 100755
--- a/horusdemodlib/__init__.py
+++ b/horusdemodlib/__init__.py
@@ -1 +1 @@
-__version__ = "0.1.21"
+__version__ = "0.2.1"
diff --git a/horusdemodlib/decoder.py b/horusdemodlib/decoder.py
index 49229ef..60b2770 100644
--- a/horusdemodlib/decoder.py
+++ b/horusdemodlib/decoder.py
@@ -269,7 +269,7 @@ if __name__ == "__main__":
     parser = argparse.ArgumentParser(description="Project Horus Binary Telemetry Decoder", formatter_class=argparse.ArgumentDefaultsHelpFormatter)
     parser.add_argument("--test", action="store_true", default=False, help="Run unit tests.")
     parser.add_argument("--update", action="store_true", default=False, help="Download latest payload ID and custom fields files before continuing.")
-    parser.add_argument("--decode", type=str, default=None, help="Attempt to decode a hexadecial packet.")
+    parser.add_argument("--decode", type=str, default=None, help="Attempt to decode a hexadecial packet supplied as an argument.")
     parser.add_argument("-v", "--verbose", action="store_true", default=False, help="Verbose output (set logging level to DEBUG)")
     args = parser.parse_args()
 
@@ -284,8 +284,14 @@ if __name__ == "__main__":
     )
 
     if args.update:
+        # Download latest list from github.
         init_payload_id_list()
         init_custom_field_list()
+    else:
+        # Use whatever is available in the current directory
+        logging.info("Using existing payload/custom-field files.")
+        init_payload_id_list(nodownload=True)
+        init_custom_field_list(nodownload=True)
     
     if args.decode is not None:
         try:
@@ -303,7 +309,7 @@ if __name__ == "__main__":
             ['horus_binary_v1', b'\x01\x12\x00\x00\x00\x23\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x1C\x9A\x95\x45', 'error'],
             ['horus_binary_v2_16byte', b'\x01\x12\x02\x00\x02\xbc\xeb!AR\x10\x00\xff\x00\xe1\x7e', ''],
             #                             id      seq_no  HH   MM  SS  lat             lon            alt     spd sat tmp bat custom data -----------------------| crc16
-            ['horus_binary_v2_32byte', b'\xFF\xFF\x12\x00\x00\x00\x23\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xe8\x82', '']
+            ['horus_binary_v2_32byte', b'\x00\x01\x02\x00\x0C\x22\x38\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\xB4\xC6', '']
         ]
 
         for _test in tests:
diff --git a/horusdemodlib/payloads.py b/horusdemodlib/payloads.py
index ae88469..c0f86f0 100644
--- a/horusdemodlib/payloads.py
+++ b/horusdemodlib/payloads.py
@@ -32,7 +32,7 @@ HORUS_CUSTOM_FIELDS = {
             ["test_int_field", "none"]
         ]
     },
-    "4FSKTEST32": {
+    "4FSKTEST-V2": {
         "struct": "<BBBBBBBBB",
         "fields": [
             ["test_field 1", "none"],
@@ -147,14 +147,18 @@ def download_latest_payload_id_list(url=PAYLOAD_ID_LIST_URL, filename=None, time
 
 
 
-def init_payload_id_list(filename="payload_id_list.txt"):
+def init_payload_id_list(filename="payload_id_list.txt", nodownload=False):
     """ Initialise and update the local payload ID list. """
 
-    _list = download_latest_payload_id_list(filename=filename)
-    if _list:
-        HORUS_PAYLOAD_LIST = _list
+    if not nodownload:
+        _list = download_latest_payload_id_list(filename=filename)
+
+        if _list:
+            HORUS_PAYLOAD_LIST = _list
+        else:
+            logging.warning("Could not download Payload ID List - attempting to use local version.")
+            HORUS_PAYLOAD_LIST = read_payload_list(filename=filename)
     else:
-        logging.warning("Could not download Payload ID List - attempting to use local version.")
         HORUS_PAYLOAD_LIST = read_payload_list(filename=filename)
     
     return HORUS_PAYLOAD_LIST
@@ -280,13 +284,17 @@ def download_latest_custom_field_list(url=HORUS_CUSTOM_FIELD_URL, filename=None,
     return _custom_field_list
 
 
-def init_custom_field_list(filename="custom_field_list.json"):
+def init_custom_field_list(filename="custom_field_list.json", nodownload=False):
     """ Initialise and update the local custom field list """
-    _list = download_latest_custom_field_list(filename=filename)
-    if _list:
-        HORUS_CUSTOM_FIELDS = _list
+
+    if not nodownload:
+        _list = download_latest_custom_field_list(filename=filename)
+        if _list:
+            HORUS_CUSTOM_FIELDS = _list
+        else:
+            logging.warning("Could not download Custom Field List - attempting to use local version.")
+            HORUS_CUSTOM_FIELDS = read_custom_field_list(filename=filename)
     else:
-        logging.warning("Could not download Custom Field List - attempting to use local version.")
         HORUS_CUSTOM_FIELDS = read_custom_field_list(filename=filename)
     
     return HORUS_CUSTOM_FIELDS
diff --git a/samples/horus_v2_100bd.raw b/samples/horus_v2_100bd.raw
new file mode 100644
index 0000000..b4b9f49
Binary files /dev/null and b/samples/horus_v2_100bd.raw differ
diff --git a/src/horus_api.c b/src/horus_api.c
index 9f14db8..6e038f8 100644
--- a/src/horus_api.c
+++ b/src/horus_api.c
@@ -499,7 +499,9 @@ int extract_horus_rtty(struct horus *hstates, char ascii_out[], int uw_loc, int
             
     /* make sure we don't overrun storage */
     
-    assert(nout <= horus_get_max_ascii_out_len(hstates));
+    if(nout > horus_get_max_ascii_out_len(hstates)){
+        return 0;
+    }
 
     hstates->crc_ok = crc_ok;
     
diff --git a/src/horus_gen_test_bits.c b/src/horus_gen_test_bits.c
index 408aa67..50de9ae 100644
--- a/src/horus_gen_test_bits.c
+++ b/src/horus_gen_test_bits.c
@@ -145,7 +145,7 @@ int main(int argc,char *argv[]) {
       /* all zeros is nastiest sequence for demod before scrambling */
       while(framecnt > 0){
         memset(&input_payload, 0, nbytes);
-        input_payload.PayloadID = 257;
+        input_payload.PayloadID = 256;
         input_payload.Hours = 12;
         input_payload.Minutes = 34;
         input_payload.Seconds = 56;