actually i resolved this myself a few days ago. there is not an option to have it open minimized but it does do it in a round-about way.
1. With X-lite open, click the "X" in the top right
2. X-Lite will minimize to the system tray
3. Right-click X-lite in the system tray and choose "Exit"
4. Opened X-lite and it now opens by default to the system tray. this also causes it to start in the system tray on Windows startup.
but yea it would be nice if there was an actual option inside the program to make this happen.