As long as the speakers will be level and the mounts are stable then i think that museum earthquake putty or blu tack would work well enough when using the crt tv type mounts which are pretty much discreet shelves.
How to mount heavy speakers on wall.
If you re mounting more than 2 speakers it will be easier to make a template out of cardboard.
But you probably going to have to screw into the speaker cabinet if you go the tv wall mount unit.
You can mount these heavy duty brackets on the wall or on your ceiling.
Each mount is made of steel aluminum alloy and can take up to 33 lbs making them ideal for heavy speakers.
They work with one hole speakers two hole speakers and keyhole speakers.
And since non powered speakers are actually not heavy at all with less than 2 00 in materials and an hour of work it s surprisingly simple to create custom brackets for mounting them on walls.
For relatively heavy over 10lbs and when you need to tilt speaker you can use lcd tv mount.
Add some in wall speaker wire and some wall plates with binding posts and you ve got a nice clean install.
I used heavy duty drywall anchors to mount mine.
This is the best solution if there are threaded holes in the back of the speaker.
Each mount reaches out 5 5 inches maximum.
Drill a 5 16 inch hole in drywall.