It was harder to drill these holes, I think it was because these joists are higher than the ones in the basement. It was hard to get leverage. At least in the crawl space I could hook my foot under a neighboring joist and pull myself into the drill. You have to keep both hands on the drill otherwise it rips from your hand. So, against my better judgement, I resorted to pushing against the joist behind me with my head and neck. After finishing a few of them with this method, I told myself not to do it again. But I did. And then my neck started to hurt and get stiff. The stiffness was weird, since it was pretty immediate. For the remaining holes, I'd be up on the ladder and Erika would push hard against me, putting one foot up on a wall when possible. This (combined with upgrading to a fresh 1" auger bit) did the trick. But I couldn't admire the work because looking upward was quickly becoming painful.
We broke out another 300' roll of PEX and got down to running it. As we expected, it's much easier to deal with this job upstairs in the house compared to in the basement and crawl spaces. Less obstructions, less sweat, less bugs, less dirt...more head room. We got most of the first circuit run but decided to quit since it was getting late.
When I woke up this morning, I could barely move my neck. It's a little better now though.