[Ambershee]

Dalek, you're not helpful - this is an ini script related issue. Have you taken a look at the ZH Emperor Overlord for reference? It doesn't have two upgrade slots, but it does carry two options.

[IraqiPeopleRocks]

  Behavior = OverlordContain ModuleTag_06 ; Like Transport, but when full, passes transport queries along to first passenger (redirects like tunnel) 
    Slots                 = 3
    DamagePercentToUnits  = 100%
    AllowInsideKindOf     = PORTABLE_STRUCTURE
    PassengersAllowedToFire = Yes
    PassengersInTurret = Yes ; My passengers ride in my turret, that's where the Firepoint bones are
    ExperienceSinkForRider = Yes ; I get the Exp for things my turret friend kills
  End

  Behavior = ProductionUpdate ModuleTag_10
     MaxQueueEntries = 2; Propaganda model is hacked to not show up.
  End

[2312222]

It's impossible to use two portable structures on one object, it doesn't matter how many slots or queue entries you set, they won't work.

The Emperor tank doesn't come with two upgrade options that are overlord related. You may upgrade to one gatling weapon, the propaganda upgrade (if there's any) isn't initiated by an overlord upgrade.