The Everest has 1250g of down and wighs in at just over 2 Kg, so you've either got the wrong bag or the wrong specification.
I've never used one, and doubt I ever will. I had the Iceline, with 300g less down and rated for general use to a "mere" -25 rather than the Everest's -40, and in the 7 years I owned it I got the zip done up all the way for a whole night on precisely one occasion, camping on snow at an estimated outside temperature of about -15. I was using base-layers as pyjamas rather than being naked, but though I did up the shoulder collar I was still toasty enough not to bother with the hood (though I wore a light fleece hat, but I am bald).
ME give a recommended upper temperature to use the Everst as -5. This is a serious piece of toasting equipment designed for high peaks and polar use and unless you really freeze in anything else or are going to the poles or up well over 5000m for an extended trip I would much suggest it's probably not a good buy. Having said that, I sold my Iceline to a pal who's happy to use it in summer where I'm suffering a bit in a Dewline, so there are people for whom it might be right, and you might be one of them. But I'd probably investigate the Iceline as marginally more sensible firsst. Apart from being too bloody hot most of the time I found it an excellent bag and replaced with a Lightline, the same basic design but 550g fill rather than 950g, I've snow-holed in Norway in the Lightline, admittedly adding a bivvi-bag and quite a few clothes (note that's the old Lightline, nearer to the current Frostline).
If you're going to get a sleeping bag like this it would be fairly ridiculous to pair it with anything less than an Exped Downmat underneath. If you don't have that order of mat already that's your first stop if you want to be warmer IMHO, as it won't cook you in warmer temperatures like the most serious expedition bags will but it will prevent leaching too much heat away into the ground when it's cold.
I used to use one on jollies when I was in the Antarctic (Halley,1987). The ones we used had no zip - not sure whether they were specials or just that they were old.
Quite nice and toasty in the normal -10 to -25 range. Coldest I used it was a bivvy out in -48, with sheepskin, Karrimat, a fairly heavy duty cotton bag cover, and wearing Helly thermals, woolly socks and a bobble hat. I had the drawcord pulled as tight as it would go, and quite often had the bobble of the hat plugging the remaining hole. It was just about OK provided I kept still. It was unpleasantly warm if you got the top bunk in a caboose, where the temperature only got down to 0 by the morning, despite the bottom bunk being more like -25.
My friend has had one of these bags for the past 12 years, every few years he gives it a good wash, thorough dry and then uses down proofing (nikwax) to bring the bag back to almost new condition, the bags doesn't have a zip which is a bit difficult to get into if you are bivvying but you just cannot get warmer, used for winter camping bivvying and my friends never had a bad word to say about it, look after it and it will last longer than your car!!! I have the ME classic 1000 which agian has lasted me close to 10 years and is still going strong, this one weighs in at 1300g and is another great bag, especially for the money, in a sale for £150.00.
