You risk too many things at low temperatures, such as molds. The yeast and bacteria in GT are of a type that loves higher heat (70-85 degrees). I've found it does well at around 80 with overhead heat that encourages bacteria growth rather than a heating pad that encourages yeast growth.
Tap: DIPA, oaked Baltic porter, XXX pale ale, dark IPA
Bottle: vanilla kombucha, oaked puh-er kombucha, blueberry kombucha,
Primary: rose hip kombucha, oaked honey and oolong kombucha, hopped kombucha brewed with green tea infused with cab. grapes