First off, you need to give your base unit 2 weapons. A real weapon, and a dummy weapon. As your PRIMARY weapon, place your "GermanDevastatorCannonGun" there. And as your SECONDARY, add this weapon:
Code:
Weapon DummyLaser
PrimaryDamage = 0.01
PrimaryDamageRadius = 0.0
AttackRange = 400.0
DamageType = ARMOR_PIERCING
DeathType = NORMAL
WeaponSpeed = 999999.0 ; dist/sec
DelayBetweenShots = 65 ; time between shots, msec
LaserName = PointDefenseLaserBeam
LaserBoneName = LASER
End
It will fire both weapons at the same time, except when force-firing upon ground.