Having compared the Xtrons and Joying range I'm still inclined to go with Joying as they have more options and support Android Auto.
Joying have two options which pique my interest, both of which I mentioned earlier. Mindful of Mark's comment about display height, I made a cardboard cutout of the 8.8" wide screen version and experimented with positioning:
Floating just in front of the vents - simple enough to mount, but looks a bit of an afterthought?
It won't fit in the aperture at the bottom, but could float just proud of the wood trim with a custom mounting panel
Up at the top. Out of the way, but I don't like this location. Its too far away for the touch screen for a start.
This is my favourite so far. Its in reach, doesn't obscure anything, is simple enough to mount, and could either float there or have a mounting pod contoured to blend in to the dash. The brains of the unit would sit in the original aperture and be connected by a ribbon cable - they specifically support this option with a longer cable available.
I initially discounted these units as pure touch screens because of no volume control, but look what I found on their web site:
This is a radio remote control which fits in a cupholder. Looking at other pics of it, I think it may be possible to shrink it a little and put it where the menu button lives. I've already relocated my menu button to under the armrest to make room for a PF double cupholder, but I might be persuaded to relinquish the extra space for a stereo control unit.
The double-din dash aperture could be repurposed to include a Brodit phone holder with USB cable to achieve charging and the connection to the head unit for Android Auto.
Obviously all of this is very dependent on the units being competently functional and sounding good of course. Based on Joying's forum, this appears to be a bit pot luck but I suspect we'll find that with all of these types of unit.
Thoughts welcome...