Tried mussel for chub on the Tees last winter. I got laughed at in the tackle shop when I mentioned it, I don't know why when you consider mussel & shrimp flavoured meat and boilies.
As it happened I didn't get a bite on them, but to be fair the water was so cold I didn't get a bite on anything else either.
I promised to try them again towards the end of the season, but F&M put pay to that idea.
I will give them and cockles a go this season on the Tees and Swale, I'm sure they'll work.
Another thought that's been tempting me for a while is peeler crab?