I age my Cabernet Sauvignon in 2.64 gallon and 5.13 gallon barrels. Typically the micro oxidation is higher because of surface area. It’s been suggested to me that shorter time in small barrels is wise to lessen the oxidative state and barrel imparting too much of its own flavor into the medium. However in my experience I prefer to keep my wine in barrel for 6-8 months with my volumes and bottle age for 4-6 months. Keep your barrels topped off and you’ll be fine. Mead will do great in barrel with lees contact but not sure how much barrel influence you would want with a delicate beverage like mead. I’m what ever you choose it will be delicious!