Larry, thanks for the comment. Good thought.
I looked at the standard equipment database. There are some odd bits as concerns volume.
Almost any item with armor > 0 has a volume, but there are oddball exceptions like the generic 20mm AA gun, with armor = 1 and no volume.
Infantry, towed field guns, fixed guns, helos, aircraft, and ships mostly have armor = 1 and volume = 999 (but a couple of river boats have volume = 100).
Most of the SP AA guns, SP SAMS, and AA guns tend to have armor and volume set to zero unless it is a vehicle that was armored, in which case a calculated volume is assigned (but the Patriot and Barak SP-SAMs have volume assignments and armor set to zero.)
Some of this may be database errors (like the 20mm AA gun). Might be something I look at with lab scenario to see if these quirks produce lopsided loss rates.