montbell super spiral #3 UL lower temp limit – pushing it?

Montbell's website shows the bag as rated

[EN TESTED]40˚F/ 4˚C(Comfort), 30˚F/ -1˚C(Lower Limit), 3˚F/ -16˚C(Extreme*)

I'm heading to Glacier National Park at the end of the week and wanted to see how far you guys would typically push these ratings.

http://www.weather.com/weather/tenday/Glacier+National+Park+MT+MTGLAC:13:US

With temps probably dropping into the mid-30s at night, do you think I'll be alright in the SS3? I'll have long underwear top+bottom, a down puffy, and a hat with me.

I'll be doing the north loop from eliz. lake to stony indian to fifty mtn to granite park.

Thanks!