Soap Bubble Carrier Prevention

Some ideas about de-fanging the "All Soap Bubble Carrier Fleet", without
needing
too many changes to the rules.

a) Limit the number of fighters that can attack 1 target. It's the
ability of
a zillion fighter groups to all attack one vessel and overwhelm its
defences
that's the problem.

b) Limit the number of fighters that can be launched to some multiple of
the
*hull boxes* of the carrier. Say 1 fighter per 2 hull boxes per turn. So
a soap-bubble
carrier capable of launching only 1 group per turn would require 12 hull
boxes,
plus the 9 mass for the hanger.

c) Make PDS more deadly vs large numbers of fighters.

One thing I've been thinking about is as follows:

Only 1 PDS can fire at a single fighter group.
Each PDS kills D6-1 fighters, or D6-3 heavy fighters.
Any PDS that misses can fire again at a target that hasn't been fired at
yet.

So a ship with 4 PDS vs 7 fighter groups can shoot at 4 fighter groups
initially.
Say it rolls 3,5,1,6. This kills 0+2+4+5 fighters. The PDS that missed
can fire
again at one of the other 2 groups that hadn't been fired at. Say it
rolls 4,
killing 3 fighters. Of the 6 attacking groups, their strengths are now
6,6,4,3,2,1.

Note that if a single fighter group had attacked, only 1 PDS could fire
at it
(so on average, it would only take 3 casualties, regardless of the
number of
defences). 

This mechanic makes fighters *less* vulnerable when used in small
quantities
vs targets with heavy defences, but *more* vulnerable to ships with only
1 PDS.

Anyone out there care to try making some PSB that will fit this
mechanic? And
anyone care to try balancing KV Scatterguns the same way? Is D6-1 too
much?
Should it be D6-2, and D6-4 for heavies, or still D6-3?