The description for starship combat discusses that small vessels are assumed to make numerous twists and turns in combat. There is reference to small vessels deciding what arc they are attacked from (excepting an opponent using Gain the Advantage), so this likewise seems to indicate that they can twist and turn enough to bring any weapons to bear throughout a turn regardless of the firing arcs of those weapons. Is this correct?

I've been wondering this myself. I suppose it could be used as a narrative device, but I'm not sure what other value it has.

I think that the pilot has to use a Fly Maneuver to change arc (position within Close). This means it could go something like;

Turn 1

PC gunner 1: I shoot the dorsal weapon at X.

PC pilot: I use a Fly maneuver to align the ventral surface towards X.

PC gunner 2: I shoot the ventral weapon at X.

Turn 2

PC gunner 2: I shoot the ventral weapon at X.

PC pilot: I use a Fly maneuver to align the dorsal surface towards X.

PC gunner 1: I shoot the dorsal weapon at X.

Note that this uses the initiative rules of allowing the slots to be floated from character to character on different turns. Presumably the bad guys could use their maneuvers to be in different arcs too, but this might require Gain the Advantage instead.