What is the best bait for these guys?

OK I know the answer, EGGS.

Guess what I am out......

What would be the next best thing for a substitute bait to use under a float?

Bright Red chartruse orange or red Jig would work

Sky-Guy

Would you prefer the jig over say sandshrimp or prawn?

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

Cool I already have some of them

I hear ya about lockjawed...

Lockjawed fish make you want to stick your head in the water and scream sometimes...
You know they are there, they are rolling all over the place, but they wont even think about biting anything you throw at them.
I think they only way you can get them to bite is to, like I said, piss them off by zipping one of those big spinners right past their nose.

Try that hole under the train trestle 300 yards upstream from the lewis bridge and bottom bounce one of those spinners through there. Tell us how you did.