hikenboot@Parallels:~/smothwall$ fdisk -lu smoothwall.img
You must set cylinders.
You can do this from the extra functions menu.

Disk smoothwall.img: 0 MB, 0 bytes
16 heads, 63 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytes

         Device Boot      Start         End      Blocks   Id  System
smoothwall.img1               1       11087        5543+  83  Linux
smoothwall.img2           11088       44351       16632   82  Linux swap / Solaris
smoothwall.img3           44352       85679       20664   83  Linux
smoothwall.img4   *       85680      163295       38808   83  Linux
hikenboot@Parallels:~/smothwall$ echo $(512*85680)
bash: 512*85680: command not found

hikenboot@Parallels:~/smothwall$ sudo mount -o loop,offset=$(echo 512*85680 | bc) -t ext3 smoothwall.img /smoothwall
hikenboot@Parallels:~/smothwall$ ls /smoothwall
bin  boot  dev  etc  home  lib  lost+found  mnt  proc  root  sbin  tmp  usr  var