The JD 71 was sold to Yetter so I presently have a Yetter 71 planter that I got a good deal on and sold my JD71 planter. It's almost an exact copy of the JD 71. Anyway, I fix my drawbar height and down pressure on the wheel and the flex arms on the side that "flex" with the planter to stay in the ground despite minor ground variation. Yours is be the same.
Your planter should "float" with the ground contour and that movement is affected by the flexing of the arms and the press wheel down pressure. I've attached the Yetter 71 owner's manual for you to read. I sold my JD 71 owner's manual with the last planter but someone here must have one. I'm sure the Yetter 71 and JD 71 are nearly identical.
Read the manual, look at your planter, check the down pressure and see what you think. I think this will change the need for for planter bands for sweet corn. Let me know what you think. I get spectacular stands of sweet corn with mine.
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What general area or region do you live? I don't know Elie.