1.5in loft will keep me warm to 35F?

1.5" is about right for 40F
Wear warm clothing, puffy, fleece, long johns, etc and sleep on a warm pad and you can push it 10F lower usually.

Enclosed shelter adds warmth too.

I have used my 40f down to 28, I was cold, it was 34 when I went to bed, mostly my feet got cold. With a warmer pad and down booties I think I would have been fairly comfortable though. But regardless, I survived fine. I was glad to get up when it got light though. Not a problem for one or two nights, I wouldnt want to spend 5 nights in a row like that though.

Well, you got mattresses so you have a warm thing to lie on. You will be in a shelter.

I agree with the 'sleep in a jacket' suggestion. You may or may not want to sleep in the jacket but I imagine you will have one with you if it will be that cold.

You will likely want to cover your head at that temperature. I usually carry a wool cap. If your jacket has an insulated hood, that should work just as well.

if u gotta put on those extra clothes to survive, i would just use a warm down bag. heavier, but so are all those clothes.

I use a summer bag plus puffy layers to extend my comfort level.

The advantage to this system is that you can wear your puffy clothing around camp or on breaks. It makes getting up for a pee more tolerable.

The shelter you use and the location of your camp for the night makes a huge difference as well.

Thanks guys. That's what I wanted to confirm… that it's 'doable'. I do have a Polartec 300 jacket, midweight bottoms and a warm beanie that I'd take with me. If needed I'll sleep in everything I have.

Since the maximum stay is two nights I think I'll survive.

@Stephen, I considered a heavier bag but down here the only times I'd use it was climbing that mountain. I got the quilt as that will be useful everywhere but on the coast.

I re-measured the loft and consistently got 1 7/8 of an inch, so just shy of 2. :)

Thanks again!