I think there is a loophole................the son just has to fail to come up with any corn production history....lost it can't prove it production.   But in this instance, the son has no history on the "new land" , so I think you could combine it with one of dad's units and use that APH for both units.   The catch is, it has to be "new land", otherwise you have to use the APH from both of them to calculate a new APH.

I do know that what we did i calculating our APH stood up to a RMA audit this past year.  I would wish one of those on anyone............

When we formed our partnership, we kept everyone yields, and they were all used to calculate a new APH for the enterprise units that we formed in each county that we farm.  (We just happen to straddle the boarder between several counties)