Well, its finished for now. I installed everything yesterday, but the D180 wasn't getting GPS data. Found some wires swapped, fixed that, but still no joy. This morning I replaced the ancient USB to serial adapter I had (bought years ago and used for all manner of lab and bench experiments) with a new one from Best Buy. That worked. I took a 45-minute test flight, got ADS-B traffic on the display, played with the flight plan, tested the AP and CDI, everything works as it should. We'll need to spend some time setting up the screen to show what we want, but that's pretty simple to do. I requested a PAPR report post-flight, because I've been making adjustments to the echoUAT threshold settings. Even that was near perfect -- 0.26% BARO ALT failures, so nothing bad.
Overall I'm happy with it. It doesn't block the radio display like I was afraid it might. I'll probably print one more mount with a few tweaks to make it more stable when using the touch screen.
Reflection from the screen is a little much to get good pictures, but not enough to make it difficult to read. A non-glare screen would have been a plus, but it's pretty low on the list of things to gripe about. It's more legible then the D180, really. I like the alerts for traffic, airspace, etc. Now the only thing left to do is figure out which AV board volume control to tweak to get the audio louder -- I can barely hear it with the iFly volume up full. Too bad you can't get at those without pulling the forward skin, that's a PITA.
TONS better than the 496, and better than the 496 and a tablet. It's a win, I'm happy with it.