Interesting!
I have an attic dipole with bent ends for 40 meters that works pretty good. About the same as a Butternut vertical that is ground mounted behind my house. I had a flat top dipole for 40 in the trees last year that worked much better. It was about 30' higher, and I suspect that was most of the difference.
I know W2DX is using high-Q loops in his attic. I work him often on 20 meters with a fair signal.
73
Bill, W4AN