I have settled on buying a Spike CF5 or CF10 Unitank. Spike shows the CF5 as best suited to 2.5 to 5 gallon batches and the CF10 for 5 to 10 gallon batches. I have the capacity to brew 10 gallon batches but in the past four years, I have only brewed four 10 gallon batches and dozens of 5 gallon...