I have a Meadowlark Petral (large speaker) on top of a Sony t.v. It hangs over several inches. I have used a combination of velcro and Blu Tack between the speaker and top of the t.v. It holds very well.
I also use 2 kinds of rubber doorstops between the overhang and the sloping part of t.v. The wedge doorstops usually used to keep doors open, I have in 3 spots under speaker, bottom side up. These rest on top of 3 half round soft stops, usually used on walls to protect from doorknobs. They have sticky paper on bottom (t.v. side) to hold them on place. These are readily available at any home improvement store.
It sounds wierd but, works very well and is very stable.
Good Luck.
I also use 2 kinds of rubber doorstops between the overhang and the sloping part of t.v. The wedge doorstops usually used to keep doors open, I have in 3 spots under speaker, bottom side up. These rest on top of 3 half round soft stops, usually used on walls to protect from doorknobs. They have sticky paper on bottom (t.v. side) to hold them on place. These are readily available at any home improvement store.
It sounds wierd but, works very well and is very stable.
Good Luck.