Japanese Bombs were also out of balance in 4.10.1 and before, just as FAB bombs.
Now they seem to be fixed:


Bomb___________kg_HE_____kg TNT_equal___________________4.10.1_Radius___4.11_R adius
Jap15_____________4.337____4.814__________________ _________30m_________15-20m
Jap50____________20_______14.89___________________ _________50m_________15-20m
Jap60____________22.68____27.51___________________ _________60m__________30m
Jap100___________44.34____38.6____________________ _________100m_________30m
Jap250__________150______166.5____________________ ________250m__________60m
Jap500__________227______247.2____________________ ________500m_________110m
Jap600__________418______507______________________ ________600m_________120m
Jap800__________382______463.275__________________ ________400m_________140m