Thanks for all your suggestions.

The Kinze KPM II  will do the planter monitoring.  No information will be fed to the Greenstar system except a planter height reading--down equals planting.  The target rate shown in the screenshot is an operator entered number for documentation purposes, not for control.  If, and this is the important if, Greenstar needs to "see" actual seed drop in order for the rate controller/swath control to work, that is not how I understood the system to work before purchasing it.

I'll give the dealer a look at this today or tomorrow.