FG comes in rolls, you can stack the rolls into a column and make an extremely powerful corner bass treatment. The rolls are densely packed for shipping so VLF can be absorbed. I use recycled cotton this way, not as densely packed and it makes so much bass I end up taking half of it away. Then my wife says get those garbage bags out of my living room then I take the rest away. Rinse and repeat about twice a year.
When I read of people wrestling with midrange echo in today's modern architectural design with big open floorplan spaces, hardwood floors, grainte countertops, leather couches, tons of windows there's no plush left to knock down some of the midrange. Rather than experiment with expensive, professionally-produced absorption panels, it is easy to throw a bunch of quilts on the floor or hang on the walls. These allow covering a large percentage of the reflective surface, albeit temporarily, enough to let you hear whether damping will help with the midrange echo before investing in professionally made treatments.
One more: if you sit in a small room with your head close to the rear wall, consider getting a single 4 x 2 BAD panel from bhphoto.com. These are 2" thick, and they sound fantastic even when your ears are inches away. BAD panel is combination of absorbtion and diffusion. (BAD = binary amplitude diffusion.) They're expensive to cover a whole room, but one pad in that key location, or for 1st reflection points (if you believe 1st reflection needs damping) is a good investment.