My method step by step (P51 with 2 2000lb bombs):
1 - Select the target from distance and fly towards it at 8K-10k. Select ".salvo 2" and the bombs.
2 - Once near the target invert your plane so you can see clearly the target centered into your up/front view.
3 - Select the top view (KP5) and keep flying inverted and leveled till the target is centered into your view.
4 - Cut throttle and dive with the target centered in your GS.
5 - At 2-3k drop the bombs and recover.