going backward to inwalls - some questions

Due to a signficant remodel, my listening room will be no more. I'm ok with that, but not without music. Because of the open configuration of the new space, I have no room for my floorstanders. So I'm going to in wall speakers (Sonance VP89). It's also a sizable space so I'm going to need a subwoofer - which also must be an in-wall.

I don't really have good places for the in-walls per se because it's an older house and exterior wall construction is 2x4 and I don't want to invade that cavity w/ backboxes.
So, my thought is to put the in-walls (in back boxes) in the shallowly sloped ceiling. I can place them such that they'll provide decent tweeter and mid-range coverage in the room. No listening chair. (Too bad because I'm sure the imaging will be stunning as I listen to the orchestra in the sky...)

1) I bought in walls models intending to put them in walls. Now they might go into the ceiling. while this is certainly not ideal, does this sound problematic to anyone?

2) the trickier part. Should I do the same with the sub (also going into a back box if I can get one).

There is a spot to place the sub in an interior wall, but I'm thinking a hutch with china will be in front of it and I think I'll hear china rattling all the time if I do that. So, because it's generally non-directional, can I put a sub in the ceiling?

3) I haven't purchased the sub yet. I'm looking at the Sonance VP12NC as it seems well designed and their VP series are better than other in-walls I've heard, but nobody stocks it so I can't audition. Given the compromises everywhere, I'm unwilling to spend up for JL Audio's version. So, any suggestions on a well designed in-wall sub?

Paradigm: they have the RVC 12SQ and PCS 82SQ but I hear their back boxes are suspect. I can install carefully enough if they're the right choice.

KEF: Has anyone heard the KEF Ci3160? It certainly won't go as low as the Sonance or Paradigm, but spec wise would probably be adequate for my purposes, particularly if I installed two of them. I don't see a back box option on the website.

Other options?

Thanks for sharing any thoughts.
Would the speakers generally be pointing at your listening position? If so I don't see a problem.

As for subs, look at Triad or Wisdom Audio or James Loudspeaker.
When you are looking at in wall applications I would give James loudspeakers a serious look . Home theater speaker manufacturers typically do a thorough job of prioritizing their designs for in wall both full range and subs. Take your time its not the same swapping out in wall speakers if they do not fit your needs . Good luck!
Thanks for the recommendations and feedback.

I'm not familiar w/ James at all, but seems like an interesting company who's thought some of these issues through. No dealers in my neck of the woods unfortunately. Same for Wisdom and Triad unfortunately. So, I'd have to buy on trust for all three manufacturers, just like for the Sonance reommended by my dealer. That said, Wisdom clearly owns the high end space so I'm sure they're great. And, probably outside of a reasonable budget based on what else I've read about the company.

The specs on the Triad sus seem...optimistic. I don't know how you'd get flat to 20hz as suggested without a bigger cabinet, and a fair amounnt of DSP processing. Of course, I don't follow specs too closely as I have a background in pro-audio and am used to a fair amount of salesmanship. But, seeing trumped up specs doesn't give me a good feeling about the company. Particulary since an audition is out.

There is a dealer for the paradigm products so I'll go listen to their subs. And, past experience w/ Paradigm (SA series) has been good.

Any others want to chime in?
It's not likely you will be happy with this setup due to room issues. It's unlikely you will be able to put the speakers in their optimal positions due to construction limitations. Set aside enough money for a great headphone system. $700-$1500 will get you superb sound through headphones.
Just an update that may be helpful to some. I have the system in and I have to say I'm very pleasantly surprised at the general fidelity of the sound. Does it image? Of course not. But, the Sonance VP89s are remarkably smooth (I have them bi-wired to Parasound Halo gear), and I bought an REL Brittania B3 sub instead of an in-wall sub so I really do have full range. BTW - I have Paradigm SA Reference in walls in a different system and while they're pretty nice, too, these Sonance are notably better. Call me pleasantly surprised.

The speakers are in the ceiling but really do sound very nice. And, i was able to stabilize things such that I don't hear the ceiling adding much to the music. Overall, a far better result than i was expecting and perfectly enjoyable for listening to my favorite symphony. And, I don't feel the need to plant myself in a listening chair, so I can just enjoy the music while I do whatever.