To be honest if I didnt have good bait I would be throwing Spinners at 'em.
I have caught some of the biggest silvers I have ever caught on the Sky using a large orange or red vibrax with a silver spinner blade.
I dont persoanlly use floats for silvers in rivers because a slowly retrieved spinner along the bottom through holding water is really effective when the fish are in. This also works when they are "lockjawed" because the spinner will tend to piss them off it you get it in their face, enticing a strike.
Use a little shrimp oil on it.
good luck.

Sky-guy