Originally Posted by MachThreeSlug

I think you get the 50 stam bonus from all of the phase 2 maps. I got it from the first map of phase 2.

That's interesting to know; unless there's an increased likelihood of getting the Secret Garden mission on the 80 stam map, then it seems like the 15 stam phase 2 map is the one to farm:

Phase 2

15 Stam: 13 fans (0.87 fans/stam)
30 Stam: 27 fans (0.9 fans/stam)
50 Stam: 45 fans (0.9 fans/stam)
80 Stam: 72 fans (0.9 fans/stam)

Getting a SG (an extra 50 stam yielding 232 fans)

15 stam map nets a total of 245 fans @3.77 fans/stam
30 stam map gives a total of 259 fans @3.24 fans/stam
50 stam map gives a total of 277 fans @2.77 fans/stam
80 stam map gives a total of 304 fans @2.34 fans/stam