You must hatch local eggs. I've only worked with chickens from near sea level to about 2,000' but I would never incubate at 50% or 65% humidity. I just used those numbers to demonstrate how molecules (O2, CO2, H2O, et al) move across membranes faster in thinner air and the need to compensate for that moisture loss.
Oxygen needs to be increased at elevation but increasing ventilation contributes to that moisture loss.
Regardless of elevation, all air contains 21% oxygen. At elevation, air pressure is lower.
Increasing ventilation partially compensates but not enough to overcome the negative of excess moisture loss. The best bet is to increase oxygen without increasing ventilation by use of an oxygen concentrator or generator.
I've been studying this for some time from the perspective of scientific research I found at commercial poultry and incubation companies like Pas Reform, The Poultry Site and Aviagen.
I've only been incubating poultry at this elevation but I've worked with psittaciformes at high elevation and plan on working with chickens there as well. I've even considered utilizing a hatchery at lower elevation to compensate so oxygen generation wouldn't be necessary.