IMPORTANT: SOLUTION
Please test this solution. Going by the advice I found on dxdev, I draw an image each frame AFTER my flip. It is a 2x2 texture.
I then lock and unlock *just the texture*. It seems to have solved the problem. Please test...
Flip 0
DrawImage antiLag,0,0
LockImage(antiLag)
UnlockImage(antiLag)
Just in case anyone missed it: please give feedback if this works for you...