Mind posting the table entry? I want to experiment with it.
Ok, here it is, but be careful with that, it really kills the framerate, and i'm not responsible for anything that might happen with your PC, use at your own risk!

I post here also my system specs, so you can compare them with yours and adjust the values in the table BEFORE launching the game.
Pentium Xeon 2.4GHz
1GB RAM
ATI Radeon HD 2600XT 512DDR3
$Name: Area Flak
$Model File: hornet.pof ;; flak weapons are invisible until
they hit or explode, so this doesn't really matter
$Mass: 1.0
$Velocity: 750.0 ;; really fast - like AA fire
$Fire Wait: 0.01 ;;
$Damage: 1
$Blast Force: 70.0
$Inner Radius: 70.0 ;; radius at which damage is full
$Outer Radius: 90.0 ;; max radius for attenuated damage
$Shockwave Speed: 0.0
$Armor Factor: 1.0
$Shield Factor: 1.0
$Subsystem Factor: 0.4
$Lifetime: 15.0
$Energy Consumed: 0.0
$Cargo Size: 1.0
$Homing: NO
$LaunchSnd: 116
$ImpactSnd: 117
+Weapon Range: 14000 ;; Limit to range at which weapon will actively
target object
$Flags: ( "Big Ship" "Flak" "particle spew" )
$Icon: iconmissile06
$Anim: LoadMissile04
$Impact Explosion: exp20
$Impact Explosion Radius: 100.0
$FOF: 40
$Shots: 60
For a spherical "effect", you'll need a ship that has turrets on all sides, AND make sure the enemy wings attack from all sides. My Cube of Doom
TM has 12 turrets on each side and was attacked by the awesome Brick of Destruction
TM ( the total polycount of all ships - at the same time in mission is around 1500 ).
I guess every (low poly) ship will work, but ya have to edit the table to turn secondaries into primaries.
With the table posted above i had 4 FPS, at high detail, Flak explosion effect, and i was 45000km away from the "action".