Those do look great! I'll have to see if I can find something similar here...I have been wanting to do corn fields, too. I just hadn't found an inexpensive option, yet. These will definitely work for settler cornfields.
Interestingly, the native Americans grew their corn differently. They would put all three of their major crops together -- the three sisters (corn, beans, squash). Hopefully, this link comes through:
I haven't figured out a good way to model that, yet...ha, ha!
Consider your idea stolen, and I am glad you like the rules!
Mike Demana
www.firstcommandwargames.com