Airborne Woes

[Akmatov]

Desire to drop US Para units post 2006 and seem to only be able to drop infantry units, even though other units are labeled 'Abn'.
For example, obat12-USA Formation 052 Abn Tank Sec. This unit has no air transport assigned according to Mobhack and the in game unit screen. I've tried:

1) buying a unit and putting in on one of the C-130s that comes with the Para Plt (A)

- the tank is invisible in the Deployment Screen and while seemingly I can load the invisible tank (the C-130 shows carrying capacity used)and it seems to drop; it remains invisible and unusable, although I seen to have air dropped its crew.

2) changing the Formation values in Mobhack so the formation has an aircraft assigned.

- same problem as above.

3) changing the Formation values in Mobhack so the formation has an aircraft assigned and set the Purchase Screen to 5 - Air Transport + Troops, imitating the settings for Formation 137 Para Platoon (A).

- the Abn Tank Sec vanishes from the Purchase Screen.

Anyone have an idea as to what I'm doing wrong?