Is it Balao? And whats the difference between first balao conning tower and second? Because if its only paint scheme, then you can move the upgrade in time:
\Data\UPCData\UPCUnitsData\UnitParts3Balao.upc
there find this section:
Code:
[UnitPart 2]
ID= BalaoConningMs32
Type= GatoConningTower ;Can only placed on unit parts slot of this type
NameDisplayable= A new paint scheme was applied to your submarine: MS 32/3SS-B
UnitPartInterval=NULL, NULL
ExternalLinkName3D= data/objects/Conning_Balao_02
HullTextureNameOverride=data/Submarine/NSS_Balao/NSS_Balao_T02.tga
HullLightmapTextureNameOverride=data/Submarine/NSS_Balao/NSS_Balao_O01.tga
HullNormalmapTextureNameOverride= NULL
MenuSilhouetteTextureNameOverride= Balao_Class_02.tga
And change UnitPartInterval=NULL, NULL to something like UnitPartInterval=1990-12-01, 1992-12-01
Maybe this will need a tweak too:
Data\Submarine\NSS_Balao\NSS_Balao.upc
Code:
[UserPlayerUnit 1.UnitPartSlot 1]
ID=BalaoConningSlot
NameDisplayable=Conning Tower Mount
Type=NULL
AcceptedTypes=GatoConningTower ;Only UnitParts of this type could be placed here
IDLinkUnitPartIntervalDefault1= NULL, 1944-04-01, BalaoConningMs9
IDLinkUnitPartIntervalDefault2= 1944-04-02, NULL, BalaoConningMs32
ExternalNodeName3D= Z01
The dates for IDLinkUnitPartIntervalDefault1 and 2 should be adjusted accordingly (?)
I am trying to point you (or someone else in this forum who may want to help) in right direction; I have no idea if this will work...