I switched my advanced order form to POST from GET as the URI request became too large for browsers to handle. Everything works fine, with the exception of will pagaination. It
You can add a param to will_paginate
https://github.com/mislav/will_paginate/wiki/API-documentation
<%= will_paginate @orders['order_items'], :params => { :method => :post } %>
If it doesn't work, set te complete controller and action to params.