UVM Extension's Agricultural Engineering Program is dedicated to enhancing Vermont's food systems through education and outreach programs focused on analysis, design, evaluation and adoption of infrastructure, technology and equipment that meets the needs of food producers and processors.
Vermont's food systems are experiencing increased localization, value addition, diversification, extension of growing season and increased market demand. Farmers and processors with specific technical education needs and research and development ideas related to Vermont food systems are encouraged to contact us.
The originator of the post / tool will have to answer that. I'd suspect purchasing 3" won't be that much more expensive and will be on the safe side. But don't have exact dimensions of 32" diam. drainage pipe in front of me. if you have the pipe, measure it and add in the batten board thickness.