Hubby is home now after a month in Indonesia and yes they saw the large school of hammerheads in the Banda Sea at Nils Desperandum Reef. Chatting with other operators whilst at sea, he found out that the hammers school was also seen at Serua, Nila, Manuk and Karang Hatta just outside Banda Neira. There are many sites where the schools can be seen (also Nusa Laut) and whilst LoBs are increasing in the area and unfortunately some still jump in on you and crowd the site, for the most part everyone works together to give their guests the best experience.
Re Solitude... a pal was on a couple of their trips out of Ambon and saw loads of hammers (photos posted on facebook), so guess they know what they are doing ;-)
We thought about Cocos but the long crossing out there and colder water put some of our buddies off so we've just booked Samambaia for 2021 for an Ambon-Ambon trip that also goes to Lucipara and Gunung Api.... there's so much more to the trip than just the hammers though... such as the gorgeous reefs at Terbang, and the sea snakes in Manuk... only 3 years to wait!