First, I don't want this conversation to turn into a "my elk is bigger/smaller than yours." That is a waste of everyone's time.
My original point was that if the animal is to be carried out solo without a horse, or, frankly, with a horse and eight people, it makes more sense to skip field dressing and skin from the backbone, deboning and carrying out the least weight. I've done it with both elk and deer, and I find it a faster, slicker method. There's less mess, and any CWD concerns are minimized. Field dressing is old fashioned and unnecessary in many cases.
However, as to your 280 pound figures (4x70=280, averaging your loads), I was intrigued, because I remembered the certainty of the lady who shipped numerous elk. She seemed to know that we hunters badly overestimate the weight of trimmed meat. I looked up my notes on the converstaion, and my memory (for once!) was correct: 125 pounds to ship an entire cut and wrapped elk. She even said some went as low as 110 pounnds.
So I called another processor this morning, basically at random: I had their phone number. It was Brothers Custom Processing in Craig, Colorado, certainly a location where many elk are killed. Their phone number is 970-824-3855, if you'd like to call them.
I basically said, "Settle a bet for me. How much does cut up, wrapped elk weigh?" With no hesitation, they said, "150 pounds." They didn't mention a range, which doesn't surprise me, because when you look at a herd of elk, you don't see some animals which are 40% larger than others: they are all about the same size, within reason. And they didn't hesitate. It was a certain answer.
Now this is admittedly 25 pounds more than the other source, but it's clearly within the range of my argument. I'll agree that you'd lose a little weight when you did the final trimming, but I don't think that's the big deal. If you take all of the bones out, the resulting load is both smaller and more compact BY FAR than a quartered animal, and weighs less than most hunters believe.
I don't doubt your word on your elk: I wasn't there and:didn't see it.
But all evidence I can find says that my basic premise is basically correct.
Again, thanks for the comments! .