I have been trying to find out about it: Whether Non-Nexus phones can use Fi service, with full knowledge of potential signal losses.
According to Fi Support chat it doesn't sound like I can move two numbers over to it. Damn.
How about porting one line to Fi and the other one to GV (on a separate GMail account). You can't forward that GV to Fi, but you could access that second line (both incoming and outgoing call/txt) from Hangouts, over data.
I think this should work, unless an actual Fi user could correct me.
I've been looking into that. My concern is the reliability of hangouts. How well does it work and what is the data & power consumption of it to be in constant wait?