In-ceiling triads for atmos .4 with hat channel ceiling
I'm looking for advice on something I'm considering. I'm finishing my basement and would like to use 4 triad ceiling speakers for the .4 dolby atmos/dts:x effects. I have two goals for sound isolation, I'm trying to decrease the amount of sound that can reach the rest of the house. I'm not looking for complete isolation, but enough so that a movie doesn't shake the the upper floors. Additionally, my son's room is right above where the HT will be. I know there is only so much I can do for his room and my goal is to be able to enjoy a sitcom at night without waking him. (not master and commander)
To help with this I am putting an isomax based hat channel system in for the ceiling. The left, front, right walls are block so I do not have any concerns with sound escaping to other adjoining rooms on the same level. Behind the listening position is an open space and a guest bedroom (also bordered by block walls).
I'm using acoustic putty for the small led lights were putting in the ceiling for lighting, but that leaves me with the in-ceiling speakers and the crux of my post.
Has has anyone ever installed a Triad speaker in a similar ceiling installation? I'm mostly concerned with the opening I would be creating in the ceiling even though the hole would be filled with a speaker. I know I must not bridge the ceiling and joists, it looks like the speakers mount to the joists in both new build and retro. I've seen websites that talk about custom built backer boxes that do not touch the joists or subfloor, I'm just wondering if the speaker's baffling is adequate and how to best mount them.
I'm also curious if anyone has installed the baffled Triad in-ceiling speakers and experienced how much sound is radiates out the back to the above floor?
I've done a fair amount of research but am having a difficult time finding this exact scenario. General concepts I've come across range from "any hole will completely negate all the work you did" to "even with can lights the sound was still significantly muted".