Can you have a mix of F/Os and tie fighters docked to a gonzanti?

Off the top of my head, I believe you cannot.

Not by my interpretation.

You may dock up to 4 TIE fighters, TIE Interceptors, TIE bombers, or TIE Advanced to this ship. All of these ships must have the same ship type.

Based on the Youngster FAQ (and E-mail rulings, if I recall correctly), essentially anytime that "TIE fighter" appears on an upgrade card, you can exchange it for "TIE/fo". However, this doesn't change the last sentence which requires them to be the same type. Even though TIE/fo's can use cards that say "TIE fighter", that still doesn't make their ship type "TIE fighter".

Casually, sure do whatever you want.

In official tournament, not with rules as written right now it would appear.

Just bring two Gozantis instead...