Those flex fans aren't generally worth a damn. While they can, repeat, can add miniscule HP they do not cool throughout the entire operating range of the engine as well as the original fan. There's a reason the stock fans work- they were engineered to depending on their specific application. Aftermarket one-size-fits-all for anything is a guess at best.

If anyone really, really needs suplemental cooling best to get an electric- yeah they make 6v.