I was able to get a data only sim from Project Fi to provide 3G connectivity in upstate New York on my No. 1 D5. I’m using the newest firmware (160915…didn’t have sim to try on previous versions) and I added the Project Fi APN (https://apn.gishan.net/settings/os_1_40_android_0_internet_and_mms_settings_for_project_fi.php). At first, I was getting 3G signal, but the device wasn’t grabbing an IP address. After trying several iterations of changes in Settings | Connect | Mobile Networks (and traveling around the state for work), it started working. The last change I made was the select Network Operators | Choose Automatically.
I’ve only had the sim in the device for a couple of days and just got it fully working tonight. The battery seems to be be on par with the drain rate before I inserted the sim (2-3 days: no wifi, no gps, lowest brightness). It’s not speedy, but I’m hoping to get Google Inbox, Hangouts and Calendar notifications.