Youre actually close enough...I was talking about a different incident but it is along the same lines.
October 1942, on Esprito Santo, there was a Lt. Ed Loberg, B-17 pilot. He took a B-17 up on recon patrol, and spotted a PBY being attacked by a Japanese H6K Mavis flying boat down below. So he jumped into the fight. He dove the B-17 almost straight down and went at it. For 45 minutes, he flew the thing like a fighter--full power, banking past 90 degrees, really going nuts with it. There was a war correspondent on board, Ira Wolfert, and he described the encounter as follows:
"During the duel, the Fort that I was on, with a bullet in one of its
motors and two holes as big as Derby hats in its wings, made tight turns
with half-rolls and banks past vertical. That is, it frequently stood
against the sea on one wing like a ballet dancer balancing on one point
and occasionally it went over even farther than that and started lifting
its belly toward the sky in a desperate effort to keep the Jap(anese plane) from
turning inside it..."
The fight ended with the Mavis, smoking, hitting the water and exploding. To date, this is, I believe the single longest dogfight in history--the longest before this was from WWI. It's also the largest "kill" of any bomber anywhere that I know of. The Mavis was a 4-engined flying boat with a wingspan almost 30 feet longer than the He-177.
On a side note, I have not been able to find anything to back up the He-177 story. The only thing I keep finding is the same cut and paste article in numerous places. I could not find any special version f the He-177 that was equipped for such a role, so if this did happen it was not a factory-built capability. But you were quite close, and it even involved the same American aircraft.....can you imagine what it must have looked like to see two heavies flying like that?!?