Your best bet is to look at the Dolby Speaker placement recommendations for laying out 5-channel and 7-channel bed layers to make your final decision.
You know your room best, and should be able to decide what compromises may work for you or not.
Keep in mind, your actual Atmos Speaker placement (the Top Speakers) kind of dictates where your LP will need to be. If those Speakers are not installed yet, then you will have a little more flexibility.
It is generally recommended that Top Front and Top Back are the most effective in a .4 Atmos layout. Almost everybody seems to agree that a properly set-up 5.x.4 will be far more effective than a poorly designed 7.x.4.
Browse our wide-range of Dolby Atmos speaker step-by-step setup guides to find the best speaker placement and configuration for your home theater.
www.dolby.com
Scroll down to see Dolby's recommendations for 7.x.4 and 5.x.4. These are Dolby's ideal placements, so remember that you can still play around a bit to get your own room setup. Of course, the closer you can stick to the recommendations, one would expect perhaps a better result.