Seperate bi wire cables?

For best results do you need to keep bi wire runs seperated from each other by an inch or so?
I run seperate bi-wire cables and keep them apart by about an inch.
I also suspend them off the ground and find that this is the best way to run bi-wires. Used to have a bi-wire terminated single cable and this was not as good with clear loss of depth and image detail
Yes. You want to provide an air space to prevent inductive EM field crosstalk.
I've wondered about this too. Since I don't have the option of separating them, I decided to twist the two pairs together with 3 twists per foot - nothing scientific. I don't know if this is a good alternative, but fortunately I don't have golden audiophile ears so I doubt I could discern any difference anyway.