Summerlite vs. Megalite

Yes!

I'm 5'9 180 lbs medium build. I wanted but had to reject the Summerlight because of the 59" shoulder girth.

It was maginally OK when lying on my side, but tight against my shoulders and elbows when lying flat with my arms alongside my body. Down compression at those points translates to cold spots.

You'll need the 64" of the Megalite, especially if you ever plan to stretch the 30° rating by wearing an insulting layer inside it.

You're in CA; find a Western Mountaining dealer and go there; try the bags on for size. I think you'll agree that the 64" girth is far more comfortable. WM makes several bags in that girth, just pick your temperature rating.

Let me recommend an alternate 64 inch girth WM bag, and the one we bought for each of us – the Sycamore MF. It is 8 oz and $10 more than the Summerlite, but is rated to 25°F, adds the microfiber shell for wind and water resistance, and being a semi-rectangular bag, has the added option of unzipping completely to form a great quilt. We often use just one for the two of us in the summer. Note that it has TWO zippers; one down the side and another across the footbox. This gives you a huge range of venting options. I usually leave the foot box unzipped at least half way so I can stick my feet out easily if they get too warm, or pump air through the closed bag tube to cool my body.

I beileve you have the bags mixed up. The Summerlite has a 59" girth. The Alpinlite has the 64" girth.

Bag girth depends on the user. I'm 5'10' 200lbs and the 59" girth bags fit me well.

I think you might do better measuring the girth of your shoulders and chest. I seem to have a girth (around my arms/shoulders) of around 49 inches. The WM ultralite long (60 inch girth) fits me nicely.

Try measuring your "girth" and maybe some others can compare theirs. It's probably more meaningful than simple height/weight ratio. I'm pretty trim so my shoulders are the widest part. Some others may find they are widest round their mid-section.

Have someone measure around your widest part when you are in sleeping position. For me, this is around my elbows as I am a back sleeper. most manufacturers don't tell you elbow girth, which is why it's best if you can actually try before you buy (wearing all the layers you might possibly wear in the real world).

Sean, I'm also looking at WM bags currently. Take Bob's recommendation. I went to a dealer and asked to lay in a 59"er. I'm a side sleeper and found the Summerlite to be JUST RIGHT. Not too much room for extras in the bag. I'm 5'11" and 190#. If you plan on wearing a bunch of layers, it could get snug inside.

Bob, I remember reading that a more water resistant shell is good for keeping out water but also good at keeping in moisture. Any noted problems of down getting damp when fully zipped up?

Can anybody else confirm the stuff that I've read?

I've used my WM MicroFiber series bag for 10 years on the PCT and never had the slightest problem with moisture in the down. I particularily like the wind-blocking quality of the MF shell.

That said, I take the opportunity to periodically air my opened bag in the sun during lunch or extended breaks. Not only does that help keep it dry, it also reduces the "funk factor" that builds up with repeated use.

Until recently I was 5'6" and ~170 pounds (thankfully lost 15, not looking for them, running in what I hope is the other direction). I fit a Summerlite perfectly. Plenty of room in there to add a down jacket if needed. Sometimes I sleep on my back, sometimes (usually) on my side; no problems whatsoever with fit, even with a down layer worn.

It's a completely personal preference. Since Bob prefers a semi-rectangular bag, it makes sense that he finds a SummerLite confining. (I have a semi-rect from WM and it is great for opening up, using for two people…) As I've said elsewhere, usually if someone is asking if something is "enough," it probably isn't. In other words, the SummerLite would fit you fine. But if you're worried about whether or not it's big enough, your expectations might well be for a bit more room.

As others have said, take/make the time to try them on! Cheers-