My VP100 is near 8ft and aimed downwards, the M60s are on the floor and the TV's bottom is at head height while sitting. The only problem I have noticed is that for certain scenes in movies when dialogue is called for from the LF or RF, it is now coming from below the TV, a minor quirk that doesn't happen very often.
Your 1804 does in fact have time delay in the form of speaker distances. Just go into the speaker setup and scroll through till you find the screen to adjust the distance. I have the 1804 as well.
If you check for some of posts lately I have the M60s currently paired with the VP150 and twin M22s for a center. These pics will show you my arrangment.
