Apparently the 1581 doesn't want sides swapped after all?

src/formats/commodore1581.textpb

@@ -16,7 +16,7 @@ layout {
 	layoutdata {
 		sector_size: 512
 		physical {
-			start_sector: 0
+			start_sector: 1
 			count: 10
 		}
 	}
@@ -31,16 +31,11 @@ encoder {
 			gap0: 80
 			gap2: 22
 			gap3: 34
-			swap_sides: true
 		}
 	}
 }
 
 decoder {
-	ibm {
-		trackdata {
-			swap_sides: false
-		}
-	}
+	ibm {}
 }