5.1 System Front Speaker Separation B&W 802D

I am moving into a new house in August and need some guidance on speakers separation. The room is 18' x 16' (5.5m x 4.9m), Front L/R speakers will be on the 18' wall. I intend to install all the speaker cabling in the wall out of sight. What is a good starting point (speaker separation) for the front B&W 802D speakers? I realize ultimately trial and error will optimize the speaker positioning, I am just looking for a good starting point for the speaker cables to come out from behind wall.

The rest of the system is all B&W; HTM2D center, N805 rear surround L/R and ASW850 sub. Power amp is a McIntosh MC207 (7x200W), I intend to bi-amp the front L/R speakers so I can use all 7 channels of the MC207.

Thanks in advance for your help/guidance.

Why does Audiogon automatically alter discussion titles containing B&W to B&W?
Yes they do come with casters. However, the speaker wires will be installed before the speakers arrive. Hence my question. I certainly intend to leave enough wire sticking out the wall so I can move the speakers up to 2-3 feet in any direction.
Why does Audiogon automatically alter discussion titles containing B&W to B&W?

It’s actually a bug in how it renders the ampersand. It’s kind of an HTML thing.  I'm sure there are probably a lot of other special characters that cause this effect, but ampersand is the most prevalent.
Well, you don’t want to go too far beyond your screen, and you don’t want to be so close to the sides you increase the side reflections.

If you are much wider than the screen the sound effects will no longer match the screen. Remember in a theater speakers are usually behind the screen itself.

I would place the front speakers no wider than 1/2 the distance from the edge of the screen to the wall, and probably 1/4 that distance to keep them close to the screen.