As far as I see, cFosSpeed uses its own NDIS Intermediate driver to shape the traffic. CPF may interfere only if you have Security->Advanced->Advanced attack detection & protection->Monitor other NDIS Protocols than TCP/IP option is selected. If so, try to disable it.
Otherwise, please tell us how exactly we should observe the behavior. I mean how do can we test if it works or not?
Because here it works ok with defaults. It improves the performance 4 times.