Can the Amp and Connect be told to output mono rather than stereo? Using with mono ceiling speakers in bathroom and kitchen.

Agreed here as well.  Mono for me would be useful so that in a kitchen/diner or a bathroom/ensuite I could have a single speaker in each and provide a 'full' sound feed rather than just a left or right.  I don't need separate volume control.

Problem is that no one from Sonos is apparently reading this, or they just don't care.

I was fairly invested in Sonos equipment at one time (in spite of their relatively huge price premium), and the lack of action on this issue made me change directions.  I ended up getting an AV receiver with multiple zones and Apple AirPlay support.  The receiver also has a mono option for zone 2 because someone there evidently realized this need.

So instead of spending a bunch of money for a dedicated Sonos amp for my back yard on top of a Sonos Connect for my main receiver and separate Sonos speakers for every room that I wanted music, I bought a new receiver that handles my living room AND my back yard, and used the Apple TVs I already had in the rooms as AirPlay devices with relatively inexpensive amplified speakers. 

Don't get me wrong - there are plenty of annoying issues with Apple AirPlay, and I would still pay a premium for Sonos, but I won't even look at them again until they address or at least respond to this issue.  If this requires hardware changes to implement, at least let us know.  If it can be done in software, then there really is no excuse for no action or response from Sonos or over 2 years.

The more you ask for, the more the engineers have to do. You are asking for the functionality of two units in one with a separate volume control. That's not cheap to do. Requires a completely new design. Mono is already available in the portables. Just needs to be added to connects. Your issue can be resolved by setting the gains differently on the power amp powering each zone. If you are using a powered connect or a standard receiver, then you have to just buy two connects. This lack of mono is killing custom installation companies like mine .
Well, Adam Brown below is asking for the exact same thing, yet uses an additional device (Non Sonos) to control the volume. Im just simply asking for your request, plus asking in addition for simple volume control, goes hand in hand with the Mono. Sonos my guess would want to keep Sonos with in Sonos. Why add more devices to something that doesnt need it. Its not even close to "Canobalizing" their sales. If so, then your simple request for Mono is what Canobalizes the sales. Mono allows for separate locations for the L/R outputs. Volume control is just a simple conjuntion with the Mono feature. Sorry you feel your idea Canobalizes their sales.

Balance. Balance is actually Volume control between the two Left and Right. Its the EXACT same idea. To make separate volume controls involves NO hardware additions. Its the simple ability of combining the Connect Amps Main Volume Control with the Balance Volume nob. I do it all the time with mine now, just have to jump into the settings to adjust it correctly. My volume/balance request in addition to Mono is a basic and simpe IFTTT procedure.

My guess is, Sonos wants to keep things with in their own devices. Plus as a consumer, we would rather purchase one device, instead of having to purchase more than one to do a simple task. Why add more devices to the mix, which cost more money... 

My request is a VERY SIMPLE, well paired request with your Mono Request. Your clients would appreciate this feature! 🙂

My original question was actually a bit simpler than that, though. I don't need separate volume control over the two outputs, as I can set that manually (or via RS232) on the d-class power amp. All I'd like is both the left and right phonos to output identical, mono-summed outputs so I can send them to different zones and (post the amp) volumes. Should be easy, but would need a software implementation. Would've thought this would be easy enough tho. Hey ho.
Just curious.. why can't you use a Y cable out of a connect into the mono power amp? You can daisy chain this to a second (or more) additional power amps as needed. This is how I feed a mono amp that drives my outdoor bell tower speaker and have had no issues.

My original question was actually a bit simpler than that, though. I don't need separate volume control over the two outputs, as I can set that manually (or via RS232) on the d-class power amp. All I'd like is both the left and right phonos to output identical, mono-summed outputs so I can send them to different zones and (post the amp) volumes. Should be easy, but would need a software implementation. Would've thought this would be easy enough tho. Hey ho.
You can't sum signals with a Y cable. You can only split. I explained this elsewhere. If it worked for you it's because the amp already has an internal mono signal summing circuit. Otherwise you'll damage the preamp. I don't think anyone at Sonos cares otherwise this post would have had a reply over the last 2 years or whenever it was posted. I'm giving up and moving on, I'll use other products when really must have mono.

My original question was actually a bit simpler than that, though. I don't need separate volume control over the two outputs, as I can set that manually (or via RS232) on the d-class power amp. All I'd like is both the left and right phonos to output identical, mono-summed outputs so I can send them to different zones and (post the amp) volumes. Should be easy, but would need a software implementation. Would've thought this would be easy enough tho. Hey ho.
I suppose if the impedance of the Connect outputs is low enough then each side could struggle trying to drive the other so I see where you might want to use a mixer or at least a few isolation resistors. I guess a software change would in fact be the cleanest way to accomplish this.

I am seriously considering ditching my 5 zone sonos setup because 3 of the zones would be much better served by dual mono. Has anyone found a good alternative?

100% Agreed. This could likely be easily accomplished in firmware/software. Why no mono option? Who knows? Sonos? Please?

I agree this should be an option, especially considering how two play units can be made a stereo pair.  this essentially turns each stereo play unit into a mono play unit.  if it can be done with a play, it can be done with a connect..

After 3 years the answers is still No. Why ? Some may ask , well it's very simple actually. Design you audio system correctly and do not ask Sonos to change their product due to your poor choices of equipment and lack of knowlegde. Anyone here who is complaining about Mono for outdoors. The correct solution is to use a connect preamp and a amplifier which can supports mono output if that's what you desire. Furthermore Sonos amps arent very powerful and suck at driving outdoor speakers in the first place. With regard to using the left output in an amplifier for one room and the right for another room. Are you people reading what you write? Your asking Sonos to basically make a 1 zone device 2 zones. It's so convoluted on many different levels. Basically because you guys are all cheap you want Sonos to reinvent the wheel for you. I'm no Sonos advocate but, they have a product for whatever you want to do. It's all there already. It's no wonder they wouldn't do this. Aside from possible limitations of design. Quit crying about this moronic feature and do it the correct way. If you want a robust outdoor speaker system your going to need amplification anyway. Get over it.