defaults write display detect
This is kind of a wild guess / work around but its something to try. Set up VNC aka screen sharing on your mac mini. Log in from another mac /computer , while the TV is off, and set the resolution while no display is attached. If you set that resultion to one that is the same as your attached TV, then when your TV powers on there should be no screen re-size after effects. This would effectively set the default no display resolution if such a thing exists.