And I was just answering.
Even as a temporary fix... I wouldn't do it. You can get better speakers for ceiling mounting and using for Atmos. The lobing/dispersion pattern is a real problem, which according to your plan is the thing you would have to deal with (rather than turning them upright).
For Atmos, you want more direct sound coming at your LP.
Standmount Speakers (bookshelves) would be better used. These do not need to be large or otherwise flashy. A majority of Atmos content is not the star of the show: it is supporting sound.
Likewise, though nice to have matching speakers, you do not really benefit from it in this situation. Surrounds, Rears, Atmos... these do not need to Timber/Voice match your Front 3.
Your aspiration is fine. Your choice to solve it by using Center speakers is far less than adequate.