Mt Baker in May - Sleep system advice needed

I'm doing a 6-day course on Mount Baker in early May.  I will bring my foam pad plus my insulated inflatable pad, which has been fine for winter camping here in the Northeast.  But for sleeping bags, I'm torn between two options and not knowing quite what conditions will be like.  Option 1 is a 15* Big Agnes down bag that sleeps a bit more like a 20* bag.  But it's roomy enough that on a cold night I could sleep in my puffy pants and jacket if needed.  I'm leaning this direction.  Option 2 is a 5* Western Mountaineering bag.  It's my wife's bag, is semi-rectangular, super warm, but takes up a crazy amount of space in my pack.  If conditions are bad, Option 2 is cozy, but I would prefer not to haul that volume and weight if I will be okay with the 15* bag.

I was there in May for a week a couple years ago. I took a 20F down quilt with a 50F synthetic quilt (equivalent to 0F). I also had puff pants and jackets. I would skip the 50F synthetic next time. Your puff pants and 20F bag are likely good for 0. Sub 0F is unlikely. Check the forecast. I would not over pack in volume or weight. You'll have a huge bag as it is for a guided weeklong course.

You will be taking the 15 degree bag as that is your bag. If you value your marriage you will not take the wife's bag regardless of the need. Next question ...

I've never used anything less than a 30 degree in PNW except for MIDDLE of winter, 20 degree should be fine, ESP if bring the puffy pants. Puffy pants, btw, will be worth their weight for hanging out in, whatever you do, definitely bring those!

Just my opinion: but the double-pad may be overkill.  I've never used that strategy in PNW, but i do see/understand the potential benofits, just not sure it's worth it.

A detail that may give more insight into better/best option is if you are base-camping or moving the camp around each night or ever couple nights.  

Enjoy, Baker is a spectacular venue.

Use the Big Agnes sleeping bag.  

Guide service gear lists are usually ridiculous and overbuilt. They cater to all people in all possible conditions, their list won't be tailored to your actual needs.

Your pad system is a common setup on big volcanoes in the PNW and will work great. Consider a 1/8" gossamer gear foam pads instead of a z-rest or thicker foam pad if your inflatable is R3 or higher. You'll save a lot of pack size. 

Remember they are going to saddle your share of heavy overbuilt group gear. 

What about your shelter. Is it a tent? With one other person? Two other people? Are you in a bivy? Are you in a floorless "mid" style tent? 

In a tent with another person/s a 20 degree bag is probably overkill (not in a bad way necessarily) and a lighter *high quality* 30 degree bag will probably be fine. You have a big puffy jacket and many layers to supplement your bag. 

In a bivy or mid a *high quality* a 20 degree bag is great. Nothing below a 20 degree bag is needed in the PacNW in spring, unless you know you are a very cold sleeper. 

For 6 days, on snow, you want double boots. Single boots absorb water and sweat during the day in the wet PacNW marine snow pack. Then freeze each night, meaning cold feet for the first portion of the day, if not the entire day. With double boots you can wear your liners inside your sleeping bag, feet go into boots warm already and the outer boots don't absorb water. This further negates the need for a ultra warm sleeping bag. To make double boots more comfortable insert insoles, that have already molded to your feet, into the liner. 

If you only have single boots get a 500ml nalgene and fill it with near boiling water each morning. Stick that down your boots with a hand/foot warmer stuffed into the toe. The external energy warms the boots so they don't steal your body heat. 

It's worth taking extra layers and/or perhaps doubling up on you waterproof pants and jackets. You'll be soaked from self arrest practice and crevasse rescue training (which will likely happen on separate days). Practicing self arrest is not kind to high quality jackets, a "sacrificial" set may be a good idea. 

A big factor in overall warmth is getting enough calories and water. Altitude often kills your appetite, even if you are feeling good. It's easy to under-eat when mountaineering. Force yourself to consume snacks every hour and eat big meals. Eat eat eat! You'll stay plenty warm if you do. 

Puffy pants are a luxury item, not a necessity. Over a six day course I would bring them, especially If you like to stargaze and socialize in camp at night. They should weigh 12 ounces. Side zips don't really matter, you won't wear them when moving. Amazon has pairs for $60 that are perfect. On a two day climb I would skip them. 

Check out polartec alpha direct pants. For me a pair of 60 or 90 weight alpha pants and hardshell pants, with easy-to-vent side zips, is all I need for my bottom half. 

Don't skimp on gloves for 6 days. Gloves always get wet and are hard to dry quickly. 2 or 3 pairs of liner gloves, 2 or 3 pairs of midweight dexterous gloves, a pair of warm gloves, and a pair of mitts would be good. Showa temres ($27) are good for self arrest day. 

You will be wishing colder temps, so you could be dryer. The PacNW is a wet place. A synthetic insulated mid layer jacket will be your MVP piece. Quick drying performance will be important for all layers and especially your base layer. Thin layers dry faster. Use a very thin base layer and add layers on top as more warmth is needed. Thick base layers are just sponges.