ZADs??? & DSII assistant application

I've recently started working on design specs for an application that
will
assist play of DSII (and later I hope to add in stuff from SGII and
FT/MT,
but one step at a time).  I've been reviewing the material in DSII, and
I
seemed to be confused a little about ZADs (Zone Air Defence).  I hope
I'm
not re-iterating something that's been brought up before - sorry if I
am,
but I can't seem to find any mention of cost or space requirements for
this
system.

Is ZAD an extension of the ADS system, there is mention of ADS several
paragraphs latter on page 42 in the Air Defense section?

There is mention in paragraph six of the above mentioned page that [...
vehicle-mounted Point Defence Systems may NOT engage aircraft...], I'm
assuming that this definitely means PDS systems can't be used, but does
this
also carry over to ADS systems.  I realize the answer may be obvious to
many
of you, but I wanted to clearify this, as it would be a pain in the rear
end
to find out that this wasn't the case after I've coded things up for the
Mac
and possibly Win32.

Thank you for your time,

Kevin Walker
sage@millcomm.com

P.S.  In the interest of making this application (if I ever finish it)
useful to others, the first part of this app will pick damage chits. 
Would
anyone find it useful if you were allowed to edit the chit mix that was
used, allowing the new mix to be saved if desired?  Included would be a
way
to recover the original chit mix, plus a warning/title that informs the
current user of which chit mix is being used.