Hi Bearfoil,
This is an interesting approach and to a small extent some Heli manufacturers have included the basic idea behind in their Heli's.
AW uses stringers on one side of the tail boom to generate some lateral 'Lift' to counter the torque. The same applies to MD with their NOTAR's.
As a sole means of countering torque, I don't know jow big that 'wing' would have to be, I'm afraid, it would have to be huge.
How big does it have to be on your model ?
The next problem could be the dynamics of the downwash, especially if gusts spoil it. Will it be possible to keep it reasonably steady with this measure alone ?
regards,
henra