I used the hardware that came in the box with the ADP-170s (interlocking steel plates and self-tapping drywall anchors). This does result in two small screw holes in the back of each speaker and two 1/4" holes in the wall. Are you seeking to not put holes in the wall, the speakers, or both? Mounting the speakers high up with holes in neither of them (and without putting holes in the wall to mount a shelf or bracket) is going to be tough. But, here's an idea:
You know those lamps that were popular in the 1950s and 60s that were mounted on a spring-loaded pole that wedged itself between the floor and ceiling? If you cut such a pole 1/4 of the way down from the ceiling, removed a section, and attached two flat padded plates on the middle ends to push against the speaker on the top and bottom, perhaps there would be sufficient support to hold the speaker in the middle when wedged against the floor and ceiling? Might take some creativity to be aesthetically pleasing, though...
There will probably be a slight difference in sound from these dipole speakers if they are not against a wall to resonate and reflect off of.