I would like to discuss Corn futures trading with someone who has been tracking it/trading it for a while. In particular the contract variances that currently exist between May, July Sept and Dec. They do not seem to be in line, either in direction or levels, far beyond the regular difference one would expect in index or metal futures. Is the current disparity due to particularities of this season crops? I am thinking of switching from May to Sept (skipping July), as I believe Gann did. What experiences have you had on the May roll-over?