SGII: Firing DFFG at infantry

Two questions here.

1.  I put 2 size two dffgs on a vehicle, can the operator choose to
    fire them seperately (using 2 actions) or together (using 1 action)?

2.  He fires at troops, am I reading things correctly that if he hits
    the troops will roll armor and he will roll a d8 for impact?  The
    impact for weapons designed for point targets doesn't depend on
    size when used against dispersed units (troops)?

Assuming these two are true the "best" use of this vehicle seems to
be to pick a problem unit and fire your DFFG's separately against
that unit.  If you achieve any casualties that's wonderful, however,
what you are expecting is at least 1 suppression and probably 2.

Am I on the right track here?

Roger