How do I get a new model by secret invention

[v.Moltke]

I tried to get a new BC - model 8- working for GE by an event in secret weapons. I used the slot with the Super-Heavy Railway Artillery for convenience. In which places do I need an entry? I did an entry in units/division/battlecruiser.txt ,db/secret weapons tech, events/secret weapons events.txt in config/unit names.csv, tech names.csv, doomsdaytext.csv, boostertext.csv. So the invention appears in its place with proper name an discription. But when I fire the event I can´t produce the BC 8. My question is, are all models activated one after another from 0 to 8 or is there an exception? That would mean I have to name my BC model 5 as model 3 and 4 are active. In my models.csv I only can find entries for BC models from 0 to 4 .
Also I cant find the entry for the event 8020 for the Super-Heavy Railway Artillery in the event_text.csv
Where is the mistake here:
# Pocket Battleship
application =
{ id = 990500
name = TECH_APP_SW_990500_NAME
desc = TECH_APP_SW_990500_DESC
position = { x =296 y = 188 }
year = 1936
# ?
component = { id = 990501 name = TECH_CMP_SW_990500_1_NAME type = naval_engineering difficulty = 5 }
# ?
component = { id = 990502 name = TECH_CMP_SW_990500_2_NAME type = naval_engineering difficulty = 6 }
# ?
component = { id = 990503 name = TECH_CMP_SW_990500_3_NAME type = naval_artillery difficulty = 6 }
# ?
component = { id = 990504 name = TECH_CMP_SW_990500_4_NAME type = electronics difficulty = 5 }
# ?
component = { id = 990505 name = TECH_CMP_SW_990500_5_NAME type = technical_efficiency difficulty = 6 double_time = yes }
required = { 5050 }
effects =
{
command = { type = scrap_model which = battlecruiser value = 3 }

command = { type = new_model which = battlecruiser value = 8 }
}
}

can anybody help me or give me a hint where to get info?