This was an interesting repair. Their were two different underlayments, some hybrid craft paper and then roofing felt. The flooring over felt was much tighter and less cupped. Ckearly the craft paper did nothing to protect the floor from moisture.
The flooring was laid over 3/4 fir decking set on the diagonal over a 2 foot crawl space. Moisture on the sub floor was 12 percent. Ive always used roofing felt, now I have a very compelling rrason to stick with it.
Also learned today that in the past 2 common was allowed to be composed of red and white oak and that currently only 3 common will come mixed. Add some good info for matching repairs.