What are your recommendations for a light/sub-900g down bag to stick inside Gore-tex bivy bag in Alps/on Cuillin Ridge - Spring/Summer and happy to supplement with baselayers, Primaloft belay jacket, hat, etc., if necessary. I've got warmer and heavier bags... Front runners are ME Helium 400, ME Zero 300, Rab Neutrino 400 and PHD Minim 400. Any strong views for/against any of these either way? Other suggestions welcome.
I've got a PHD Minim 400 and have found it is superb. I used it in the Fish River Canyon where night time (desert) temps dropped to between 0 and +5 degrees and was never cold. I use it now for everything except winter camping.
It is very light and packs up very small. The best bag I've ever owned and well worth the price tag.
If you ring PHD they will make it to order with choice of no zip, half zip or full zip and will ask what side you want the zip.
I don't know about the Alps - it may not be warm enough for camping high, but ideal for the Cuillin Ridge in Summer where I have also used mine.
I have a Neutrino 600 and it is very comfy but fairly narrow. I'm 6 foot with fairly broad shoulders. I fit but it is snug, I can't wiggle an arm out if the bag is zipped up, which can be annoying. Also the zip doesn't go right to the bottom, which means if you're a little too warm you can't vent your feet in a controlled way.
I have a 600 gram bag, which is way too warm for spring/summer
For summer camping I use my 250 gram bag, which is fine in the valley and good enough higher up in the mountains when combined with some clothing and a bivybag. It weighs in at 650 grams and packs down to the size of a large grapefruit.