The shape of H/K is directly linked to the "jump" between K old crop and N new crop. The bigger the jump is, the more you are likely to see H/K flat or even inverted, independently from the level of actual stocks. On the other side, Z/H is purely a storage and stocks play, so IMO the most straightforward way to eliminate the curvature risk is to make a +H-2*K+N butterfly. The risk is that the intercrop spread get even bigger because of the current shape of wheat crops around the globe( Think Russia, Australia, Germany ), but they are close to being fully harvested and wheat is already expensive. So it might be a good idea.
I chose to simply do the H/K because it is close to historical carry( VSR can go further but...) and the world will lack 12% protein soon ( according to a "physical" friend ).
I don't trade options, so I don't know if there are some better way to hedge using them.