Regarding the placement question, personally in heavy clay I like the application systems such as the Totally Tubular that use all steel components to put the popup in under the seed for 2 reasons: 1) no plastic between the vee openers  2) in my heavy wet sticky clays and especially in notill corn on corn the plastic can build up with mud and end up looking like turkey drumsticks dragging seed out of position. jmho and experience. Jim at Dawn