In the 'Settings' dialog, place the textbox below (instead of after) the following text:
ISO extraction command (%S is ISO file, %D is directory):
This box is currently, not that big. It would be easier to add a custom extraction command if you can see the whole line that you type at once (so no need to scroll in the textbox itself).
The box for 'Select the 7-zip executable' may also be a bit longer.
At least this is the case in Ubuntu 8.04:
- Linux i386 2.6.24-16-generic
- GNU Classpath 1.4.2
Maybe you can use 2 radiobuttons instead of the checkbox below the 'Extracting ISO' text:
o Use 7-zip to extract the ISO images
____Select the 7-zip executable:
o Custom extract command
____ISO extraction command (%S is ISO file, %D is directory):