An extra quart? That doesn't sound unreasonable. Running slow changes a lot of things. Total proof gallons might be a bit higher running slow, but if time really isn't an object, quality can be much much better. I spend a lot of time and electricity cleaning up rough spirit on a small 3L countertop setup. The final product is smooth and clean but it takes time. IME, my mini setup produces much nicer finished product than my 11G setup is capable of at any speed.
My tabletop setup is an Erlenmeyer flask, some copper coil from home Depot, a hot plate and a computer fan. As stupid as it sounds, it makes some really nice product.
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