I think the 180 certainly is enough for the Stearman. I have a pumped 1.20 FS in mine and have had reports of that size doing quite nicely.
Regarding the aileron servos, I have the slaved setup for now. I moved the slave rod outwards a bit in the upper wing till I got the recommended throws. I did this because I like the scale look of it and didn't like the exposed servos in the upper wing.
You should have no problem either method.
It's a beautiful plane!