In shallow hard running water I've watched a bunch of fish spook from the shadow cast by a suspended clear intermediate line (the bayside flats, with the high sun behind you, offers some great visibility for observation). Same with the floater, obviously. I'd been contemplating screwing around with a Cortland QD for quite awhile for high sun flats and did it last year. After a frustrating, windy, day casting to a ton of fish with a floater I went to the qd the next day and had a rediculously easy time of it hooking up. Presentation was to lead the fish by a long way anticipating thier path. Not much finesse but effective. Doesn't do much for honing your flatz skills though. This coming season I'm going to play with the floater and super length leaders. Bottom line (pun intended) in high sun I believe the shadow cast by the line, not the line, is the spook culpert.