A full-sized pack weighs more for day hunts but with a light load it really doesn't matter and the extra weight on a day hunt is offset by the weight savings of not packing an extra pack with your full load.
I'm a bit of a pack nerd so I want to point out that the Kuiu Ultra 3000 weighs about 3 pounds empty and the Exo Mountain 3500 weighs roughly 5 pounds - either hauls elk quarters just fine. Kifaru and lots of other 2000-4000 c.i. packs can be found in the 3-6 pound range too but some require the meat to be carried in the main compartment or strapped to the outside of the bag away from the frame.
Eberlestock packs are beasts, some pushing 10 pounds empty with accessories, but I've had half an elk (front/rear/straps) in a Warhammer at least 3 times that I remember and it was reasonably comfortable, all things considered. I've had half an elk on a Kelty Cache Hauler (external frame) twice and it was doable, but not as comfortable and the external frame sucks for going under branches when you have to duck an extra 4-6 inches with 120# on your back.
For comparison, a Badlands Ultraday is 1800 c.i. and a hair over 3 pounds, a Superday is 1950ci and almost 5 pounds. A Tenzing 2220 is 4 pounds. None of those 3 "day packs" are what I would consider functional for hauling an elk quarter, are no lighter than packs that can, have less room for gear, and in my experience with them the Ultraday and Tenzing are less comfortable to wear all day than something with a real waist belt. The biggest advantages of the day packs are price and physical size.
