Cathedral Ceiling and bulkhead

We are currently buliding a house with cathedral ceilings running the length of the kitchen, family, dining and patio. We have the kitchen making and L shape along the back wall and some of the side wall, and a island bench parallel to the back wall. In the corner of the L we have a walk in pantry. The builder suggested we have a bulkhead otherwise the flute of the rangehood would have to be super long, beacuse of the ceiling. However he said that we would have to put a 30mm piece of the reflex laminate (used for the cupboards) between the gyprock bulkhead and cupboard. Im not entirely sure why we have to do that and not have a minimal gap between the bulkhead and cupboard. Any explanations or suggestion on cathedral ceilings and bulkheads would be greatly appreciated.

Hi Jess, we have raked ceilings in the main area and above the kitchen. We put a bulkhead in over the bench for the reason that the rangehood doesnt go up forever Our overheads will have a gap between the top and the bulkhead cos I thought it would look funny having them go all the way up. Cant show any pics cos we havent even started building yet. What r u doing with aircon and heating with the raked ceilings???

We have a raked ceiling over the kitchen and for our situation, a bulkhead would just be too big. My husband is going to get a flue cover made after handover by a stainless steel fabrication joint. (He really likes and wants the chimney look.) The other option would be to get a flue cover made and then paint it the same colour as the walls. I have lived in one rental where the flue cover was just a painted PVC pipe - it was pretty unobtrusive.