I caught some of those Blackwaters at East as well. While working with Phil Rowley at the fly show he told me that the booby fly works well on them because of their aggressive nature. Now as for witnessing takes in clear water with no visible take on an indicator, I've witnessed the same in much shallower water, from 15' up to 2' deep. Same observation without the visible take. The first time I witnessed it was at Rocky Ford while fishing an unweighted and unindicatored nymph years ago. I would watch fish open their mouths take in the fly and spit it back out again faster than I could respond without ever feeling the take. This was fishing with less than 4' of line out of the rod and a max of 9' of leader. I know that fish sometimes just take the fly, regardless of what we do, without us ever noticing. I like the extra buoyancy of the larger indicators even in the wind, because they provide an extra bounce to the fly. They are also once again easier for me anyway to see and detect smaller changes in larger waves and aren't "lost" in wave sets. Lastly I like to make sure that my indicators are two tone versus single tone. This again allows for the ability to detect subtler changes.