The hack works. Quick note that you can specify the loop device in both lines, which is a little safer than assuming loop0 i.e.
/media/USBDISK/.fs.ext3 /media/USBDISK/fs ext2 defaults,noauto,loop=/dev/loop3,user,exec 0 0 /dev/loop3 /media/USBDISK/fs ext2 defaults,noauto,loop=/dev/loop3,user,exec 0 0
The hack works. Quick note that you can specify the loop device in both lines, which is a little safer than assuming loop0 i.e.
/media/ USBDISK/ .fs.ext3 /media/USBDISK/fs ext2 defaults, noauto, loop=/dev/ loop3,user, exec 0 0 noauto, loop=/dev/ loop3,user, exec 0 0
/dev/loop3 /media/USBDISK/fs ext2 defaults,