WM Megalite 30 + Jacks R’ Better Shenandoah Quilt = winter bag?

i've used megalite with ee 20 rvx up by donner in 0F and at 15F. It works but woke up several times with cold penetrating thru bag. It's pretty tough to keep it all in place but you'll be fine. After last winter I bought a 0F bag at a steep discount.

I've used a WM Hilite (35) inside of a Marmot helium (15), sort of my summer + mountains = winter bag solution. Seems to work, but haven't tested it down to its limit. Good to at least 5, I would guess. Also a no-fiddling 2 mummy solution.

Jacks-R-Better has or had a page with a formula for combining tarps/bags.

I find that wearing a down hoodie adds a lot of warmth if it isn't getting squished to much by a tight bag.

A quilt should perform as well as a sleeping bag if it is attached to your sleeping pad properly.

Of course you will want to have a good amount of ground insulation as well.

Here is the formula that was posted on Hammockforums.net by Pan from Jacks-R-Better:

First estimate take the send bag reating subtract it from 70, devide that number by two and then subtract it from the first bag rate for a combined value ex

Two 40 degre bags… 70-40 =30 devided by 2 =15 subtracted from other bag 40-15=25 for a first cut estimate of the combined bags… it may actually be better but probably not worse, so this works as a good conservative estimator, IMHO.

Pan

You could also just try adding the lofts, minus a safety factor – then compare loft with temperature ratings. Of course the bags have to fit comfortably inside each other with minimum compression for this to be reasonable.

Great information, folks. Exactly what I was looking for – a formula. Now if I was only smart enough to use it! Kidding. I the two bags may work as a short term option.