Too much distance between the charging pad and the reciever. Also I think the maximum charging rate is ~500mA, which would lead to your drone getting charged in 3 hours.
I was also thinking about it. Yes it needed to be very close and the coil might be too clumsy to be mounted underneath and could also block the sensors. You could use one of those magnetic usb cables/plugs or salvage a magsafe plug and mount it with a rubber band on your landing site.