Yes, I'm aware of the problems with collared catskill flies, I haven't use them for many years either, I always tie and use parachutes and comparaduns for that reason. This is a different situation, we are trying to get only part of the fly to sink, not all of it. Even when I've tied them parachute (clickhammer?) style, forward wing, or with CDC the butt of the fly doesn't want to brake the film. This is just the problem I've encountered with very small flies. I'd still like to know if there is a difference in the surface tension of different waters, I would think there is, but don't know if it would make that much difference for what we're talking about.