Had an 8/15 Kinze, then a 12/23.  Both box planters.  The 12/23 is traded for a 16/31 center fill, but with planter logistics we haven't got it yet.  It takes about 30 minutes to fill the 12/23 box planter from the tender and that's if you're going back and putting graphite in before shutting it all back up.  Tender we use we have to pull up one to reach the other half also.  Figure at least 3 fills a day, that's an hour and a half filling instead of planting.  Could probably cut the fill time by quite a bit and spend more time planting with the center fill.  Biggest thing with the box planters was even weight distribution, but now with hydraulic down force and the even weight distribution that pretty much eliminates that advantage.  We haven't planted corn with either of them, only beans.  Plant the corn with a 24 row Deere.