The completely lacklustre A-20 boston is irrelevant in the current Soviet tree, surpassed by Pe-2s and Il2/10 in terms of capability.
Its historical loadout is correct: at best 4x 227kg could be fitted for the DB-7
The original DB-7/Boston III/A-20A/B/C had only 4 fittings inside the bomb bay, greatly reducing bomb load when smaller bombs were fitted. The maximunm internal bomb load was reached when 4 x 227 kg bombs were loaded. Besides, Soviet bombs didn’t fit well to the original suspension points.
However modifications were quickly produced rapidly increasing its combat capability;
The Soviet Factory n.43 modified the B-3 supplied to S.U. in summer 1942:
- bomb boxes KD-2-439 were installed into the bomb bay, 2 in the front and 2 in the rear part of it. Each bomb box was for 4x100kg overposed bombs;
- it was installed the electrical bomb release trigger ESBR-3p;
- the rather primitive original Wimperis D-8 type was replaced with Soviet bombsight OPB-1 (daylight) and NKPB-4 (night).
Conclusion: Utterly irrelevant in BR3 either change its loadout to historical 8/12/16x 100kg (with associated BR increase to 4/5) or lower its current BR to 2 since it does not compete with even Su-2