[Deathsight]

It's not really about the auto pilot, but it's about the level stabiliser, just assign a key to it, that way you should be able to fly straight level and you could use the bomb sight, until your bombs get dropped.

At least it worked for me in this case,

But one more fun thing to do would be to stick around in the bomb sight until the bombs hit on impact and watching them destroy the target, even though you might have more chance of being shot down by the AA guns or enemy fighters.