Rooftop cargo noise reduction

[mbaskette]

I place this topic in the "60" forum as this is the vehicle I seek advice. If there is a better forum section, please move as needed:

I am operating a 2013 XC60 with OEM Square Profile load bars. I chose these as we already had a Thule bicycle roof setup for my 2000 V70XC and a Sears Sport 20-SV Cargo topper. The cargo topper never generated offensive noise on the V70 even without a faring. However, without a faring, this cargo topper on the XC60 produces noise that is quite unbearable. Like riding in a helicopter unbearable. A combination of airflow and the extra large sunroof which lessens the overhead sound insulation I suspect.

In preparation for our next long road trip, I have added a Thule faring to the mix. Road tested the setup last night at interstate speeds and the noise was reduced to a level that we can hopefully live with, but I would like to optimize this to see if it can be further reduced. Even with this large cargo box, there is quite a bit of latitude on where the box can be placed front to rear and still not obstruct the rear hatch. Should I place the box as far forward or to the rear as possible??

I am also curious about somehow filling the space under the cargo box, has anyone ever tried something like that?

Thanks
Mike Baskette