Cottonwood stays wet forever until you split. Firewood size splits (smaller than yours) are often well below 20% MC in 2 months after I split and stack. Might be worth at least quartering those chunks to dry them out.
It looks entirely too hilly in your part of the state. I'm a couple hours north and it's flat like a pancake. I have to remind myself that the whole state isn't just a continuous corn field. The project looks great so far!