At first we need to modify the Basic.cfg
1.Open the file.
2. Use Ctrl F hotkey and enter XXI to find the parameters related to the type XXI sub.
3. Change the Year0=1943 parameter in the [SUBMARINE3] section to Year0=1939. The type XXI is the "third" submarine elsewhere.
4.Find the ;[SUBMARINE_AMMO11];XXI section.
5. Change the NbYears=3 parameter. If we want to use the type XXI from 1939 to 1945 change it from 3 to 7 years. It's really significant!
6.Now we need to specify the type XXI equipment for EACH of 7 years. To do it simply copy this section:
Year0=1943
ForeTube40=9
ForeTube41=9
ForeTube42=9
ForeTube43=9
ForeTube44=9
ForeTube45=9
ForeResIntern40=9
ForeResIntern41=9
ForeResIntern42=9
ForeResIntern43=9
ForeResIntern44=9
ForeResIntern45=9
ForeResIntern46=9
ForeResIntern47=9
ForeResIntern48=9
ForeResIntern49=9
ForeResIntern410=9
ForeResIntern411=9
ForeResIntern412=9
ForeResIntern413=9
ForeResIntern414=9
ForeResIntern415=9
ForeResIntern416=9
Z01_40=12 ; IX/3
A01_40=9
A02_40=9
SuperCharger_40=-1
Snorkel_40=1262
Batteries_40=1269
AftBatteries_40=1269
Hydrophone_40=1272
Sonar_40=1274
Radar_40=1278
RadarWarningReceiver_40=1282
Decoy_Launcher_40=1287
SonarCoatings_40=1303
RadarCoatings_40=1305
Renown4=30000
paste this section just befor the original 1943 year section and change the
Year0=1943 string to Year0=1939
Paste the section once more next to the new 1939 year section
and change Year0=1943 string to Year1=1940 string. Repeat this operation for all years. For 1943, 1944 and 1945 years simply change the Year{x} numbers
From Year0=1943 to Year4=1943
From Year1=1944 to Year5=1944
From Year2=1945 to Year6=1945
If you want have the 1945 year equipment in 1939
copy the 1945 year section instead the 1943 year section.