Yes, of course. Good point. As soon as I saw that it didn't work, I tried the exact opposite, but it doesn't work either. It's often like this, because of commissions and spread costs.
Besides that, I've tried all the other things I have mentioned earlier: entering a few hours earlier than the close and going short, and viceversa. Entering early on monday and staying long for a few hours, and viceversa. And more. I've tested it on bond futures, and Dow Jones.