Screen sharing default observer mode

I have several .vncloc files what contains lines such:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://ift.tt/vvUEPL">
<plist version="1.0">
<dict>
    <key>URL</key>
    <string>http://ift.tt/17kV6oz;
</dict>
</plist>

e.g., double click on the file starts the Screen Sharing.app, and connect to the defined vnc URL.

By default it connects in control mode and I need switch manually to the observer mode.

It is possible to add something to the .vncloc file, to connect in the observer mode by default?