Glad to see this thread... I'm working with corn and have trouble getting over 1.045 og. I've tried different size grind, adjusted water/corn ratios, used commercial enzymes and not much has change.
In my latest batch I ground it to a fine meal, mixed corn to water at 3:1, cooked to ~180f added alpha-amylase, cooled to ~140f added gluco-amylase and still the OG was a shade under 1.045.