Ok, try to help a bit more.
If you can get 2 pairs of Totem Beak, it will be best. Due to size of ATC 50 or 100, 2 pairs really should be necessary, consider that they are about 1% of the price of speakers, and they add 5-8% performance, well worth it! Imagine the top of ATC SCM50 having 4 quadrants, my favorite position is putting the beaks in the inner side front, and outer side back quadrants.
Here's a picture of the Totem Beak:
http://www.totemacoustic.com/NewFiles/beak.html
For those having no Blue Tak around, I find the QuakeHold available in Home Depot a nice alternative. The thing is on some other goos, they will discolor and damage the wood finish, or not pliable. Make sure you roll a big enough ball, I would say, 1 slab of Quake Hold cut into 3 or 4 pieces, and roll up, stick between the factory stands and the bottom of the ATC would be fine.
Quake Hold:
http://www.quakehold.com/quakehold/showdetails/images/88111front.jpg
I used 3 pieces, 1 below the woofer, and 2 behind, in a triangle. Quake Hold or Blue Tak instead of the factory adds a tonne of air, and midrange jumps out instead of hiding. I have been using the solution with SCM20 stand mounted, so when I got the SCM50, I was stunned by the defficiency of factory recommended setup.
ATC owners are welcome to send me e-mail. I have used ATC for so long, will be glad to help.