Make a center line from the center of the TV to the center of the MLP. All sets of speakers should be equal distance from the center line.
However, if your AVR can set the speaker distance individually, and has room correction software, then theoretically, you could stagger the distance(s).
I like symmetry, so I recommend my first statement...but you have to work with the space you have.
Lastly, in-ceiling speakers are permanent...mostly, so make sure you place them where they will be most beneficial for future use. IOW, make sure that is where your MLP will be for the foreseeable future.