Hello Paul:
Reducing the size of the register will limit the air flow, reducing the heat and air conditioning available to the kitchen. To me, the most important thing about an under cabinet (preferably under the sink) register is the benefit of keeping the water and drain from freezing.
Perhaps you will have another register in the kitchen, which could make up for the smaller size. I don't remember a register the size you have quoted.
Another option is to use the 2" round vents that pop in the hole and are directional. Use as many as you want and direct them to the needed places.
Glenn
|