Despite my earlier thoughts, I went ahead with two sided printing on California Form 540. There were no problems and my refund was electronically deposited into my checking account three weeks after mailing the return.
I used the fill-in pdf forms and their scanner seems to capture the data without problem despite folds in the paper.
One interesting surprise was mailing the return on 3-21-19 but having my online account with the Franchise Tax Board showing the date filed as 3-15-19. Their scanner must have picked up that date which I had filled in on the pdf form next to my signature.