Decent flush-mounted rears

[Nimby]

Hi

I'm still frustrated by my situation with regards to rear speakers.

I listen (and watch) across an attic rather than along the ridgeline.

My fixed seating position places my head rather close to the 45 degree sloping ceiling for box rears to work very well.

I place my old Kans on their backs pointing upwards to bounce sound off the sloping ceiling. But true surround sound it really isn't.

Can I do better with flush mounted speakers?

I need at least 80Hz extension.

Any other thoughts?

Fronts are Mission 753Fs.

Thanks