i'd imagine that the compact spare won't fit over bigger front brakes, right? Anyone tried? I've never gotten a flat tire, but i don't want to get stuck out somewhere if i can avoid it.

I have a 5th RX on order for that purpose. doesn't help in the winter though, and both the flats I've gotten have been left-front

Definitely highly recommended to run a full size spare- 2 hours on I-95 with the mini spare on while trying to not get rear ended by traffic going 20MPH faster was plenty to convince me.

Get a flat in front?

Swap wheel from rear.

Put mini on rear.

Yeah, I smart like that. :)