If your application does not need ISO data streaming, you may take a look at the winusb driver. This driver works great, is available on all Windows versions since XP and is already signed by MS. You have to sign your inf file only for use under x64 Windows. No WHQL test is needed, but possible.
have a look here: www.braintechnology.de
we have expirience with whql and the FX2, we made allready WHQL Drivers for the FX2.