Baitstation is not a specific mark in any case, more a broad area from what I know. I think you were about right spot, its not in 400 fa rather around shelf line. You got a marlin so I reckon that means you were in exactly the right spot!!
I'd agree it is not the kind of place you just rock up to like Hawaii etc. would be hard going without a booking and having everything organised for you, aside from the great fishing there is not much to the place.
I'm sure some of them would have days here and there free at shorter notice but the good guys book up in prime time.
Cheers
Andrew