I'm a big fan of hot glue too, I've got a near-antique craftsman 160 watt glue gun made out of a generous amount of Bakelite with a rubber cord real nice, with a double wide trigger.
anyways- I've never even attempted to cut t-molding slots without a slot cutter. Anyways, i think it's 0.070 inches which is between 1/16 and 5/64. Opitmal depth: 3/8 inches