This doesn't help answer your question, but I will say that I had a hard time with altitude change while in Montana. The biggest problem was being tired, couldn't breath, and chapped lips from sucking air. This lasted a few days. The worst I had felt was when the first replier above (initials are 25C

)shot an elk at the highest point of the trip, which was probably less than 10,000', and while skinning, I had an absolutely horrible headache and started getting sick. It probably didn't take 500-1000' drop in elevation and it immediately went away. Which goes along with the advice of dropping altitude if you do get sick.
The next day, I had finally acclimated and was perfectly fine.
Drink as much water as you can, and as little coffee for a few days before. And I haven't heard anyone mention this, but take some unscented chap stick! You'll thank me later!