507.2.2 exception 3 exempts a single light duty convection oven from hood requirements altogether. Move it out from under the hood.
Lacking specific code text that states it, my opinion would be not to mix appliances under the hood anyway (that is, if it requires a type 1 hood, put it under a type one hood; if it requires a type 2 hood, put it under a type 2 hood. Problem solved).
507.2.2 Type II hoods.
Type II hoods shall be installed where cooking or dishwashing appliances produce heat, steam, or products of combustion and do not produce grease or smoke, such as steamers, kettles, pasta cookers and dishwashing machines.
Exceptions:1. Under-counter-type commercial dishwashing machines.2. A Type II hood is not required for dishwashers and potwashers that are provided with heat and water vapor exhaust systems that are supplied by the appliance manufacturer and are installed in accordance with the manufacturer’s instructions.3. A single light-duty electric convection, bread, retherm or microwave oven. The additional heat and moisture loads generated by such appliances shall be accounted for in the design of the HVAC system.4. A Type II hood is not required for the following electrically heated appliances: toasters, steam tables, popcorn poppers, hot dog cookers, coffee makers, rice cookers, egg cookers, holding/warming ovens. The additional heat and moisture loads generated by such appliances shall be accounted for in the design of the HVAC system.