How to make built-in installer work with firewalls that do not suport SFTP

Built-in installer in v3.0.2 uses scp to copy generated firewall script to the firewall. On Windows I recommend putty as ssh client, which includes utility pscp.exe that is their equivalent of scp. I am told ssh server in some embedded firewalls may not work with pscp.exe right away. One example is DDWRT, the error you get looks like this:

sh: /usr/libexec/sftp-server: not found
unable to initialise SFTP: could not connect
SSH session terminated, exit status: 1

To get around this, enter command line option -scp" in the "Additional command line parameters for scp" input field in the "Installer" tab of the firewall object dialog, visible at the bottom of the screenshot here.