Ditto Matt above, with reference to Mr Mellon sharing with us what his reasons, or reasonings are, insofar as he can.
Yes, we may eventually see those reasons in the lawsuit filing. But this forum being the more knowledgeable group of people on the AE search, maybe we can convince him otherwise, or maybe he can convince us. ( The "we" does not include me as I am a new poster although I have been following this site for a while). The lawsuit filing itself shows that Mr. Mellon must feel strongly that evidence has been overlooked. Not being privy to discussions between the two parties, if any, this forum seems to me the most logical avenue for a public discussion of his reasons, especially since he is a valued participant here. Anyway, I hope there are behind the scene discussions going on which can lead to a satisfactory settlement for all.
Also as an introduction and comment from a new poster, I lean towards the Niku hypothesis based on the 1) the logic of the 157/337 path to Niku, 2) the verified radio transmissions, 3) the bones discovery, 4) the 7 site and its fire features, 5) Nessie.
The single most remarkable thing which struck me was Gallagher's message to his superior on the bones discovery. He uses the words "bones... possibly of Amelia Earharts", which is a statement not made lightly by a well educated civil service officer. We don't know what else he saw, other than the bones, sextant, shoes etc. that made him say that. But the scene/discovery must have made an impression on him, to connect it to AE. I know, this is pretty unscientific, but this contemporary account of his, which could be dismissed as a wild speculation, is one of the reasons for my leanings.