A 5 pounder with a double sided tape!!!!!, not a good idea, imagine, if the spks fall from that height!!!!.
I did something similar for my spks (I dont remember the weight, but must be close), but in a different way. I build a U-shaped metal clamp with holes for screws on both ends. One side was screwed in to the TV (through the same screw, which holds the casing of the TV) and the other side was screwed to the spks (using the screw for the wall mount), in your case it would be for the floor mount.
But doing anything else with glues and tapes can be dangerous for your spks life.