I think that James has the definition of the whole nine yards sussed.
If someone is sussed, they are clever and know a lot about something such as clothes, pop music, or politics. = smart. knowing all about someone or something
If you suss a person or situation, you realize or work out what their real character or nature is. I think I've sussed the reason for it The women began to suss that there was no reason why they should be impressed by him We're getting the problem sussed. Suss out means the same as suss. They're sussing out the area to see how strong the police presence is He susses his colleagues out and he knows who he can trust I'd had the training to suss out what he was up to. to realize or discover something, or to find out the things that you need to know about someone or something