The idea of of concentric induction rings to even the resulting heat sounds simple, but it’s not. This is mostly a safety and detector issue. Assuming you design the coils so they do not interfere with each other or excite the pan beyond its ability to stay in shape and hold together, you definitely do not want an active coil operating outside the circumference of any given pan.
Have you tried setting Power Boil with progressively smaller pans? Below a certain size I expect you won’t be able to even use that mode. You may be able to spoof it into working with multiple pans, though, depending on where the detectors are located.
I actually noticed the outer area of the large hob didn’t activate for my Lagostina 28cm frypan today on power boil, just the small donut of the inner 18cm. It’s disc is a bit shy of 22cm in the exterior bottom.
My Zwilling Prime disc saute with 23,5cm bottom worked.
My Falk 24 saute has worked, though I could see the power boil was not so optimal anymore on it, lacking in power.
According to the manual the larger wattages from the dual hob are for bottoms 245mm upwards.
Also the Falk 24cm frypan seemed to “work” on power boil, but needed to be very well centered, it would probably not work in practise for cooking there. I would use the 24cm frypan on the smaller hobs anyway, its fine there. The 24cm saute I would rather use on the larger one in cooking if it still works in practise there, at least it clearly did well for reheating soup with bubbling around the edges.
I have tried heating a de Buyer 28cm frypan with 20,5cm flat exterior bottom, but more with the sloping sides and it has appeared to work also there. This pan would mostly go the 21cm hobs also though and could have similar issues as the Falk 24cm in keeping centered.
I had also wondered that perhaps its not so wise to even attempt using some real edge cases like the Falk 24cm frypan and the de Buyer on the large hob, when it comes to the pans staying in shape. Also if they are not centered, the resulting heat could be a bit all over the place for cooking, too.
