I've got a BVM Viper converted to EDF(Tams Dynamax) and have pretty much the same ducting as the ICDF version. There the outlet is 3.75in and the inlets appear to be at least 100% FSA. Probably right at 100% FSA and larger than today's state of the art performance EDFs like the Electra. Theuns sounds like you are getting 7lbs of thrust but if you want perf go EDF(I think there is a JetFan that will work very well). There is just no comparison to the old ICDF even if you expand the outlet. Of course the runtime of ICDF is still superior vs EDF...