Leakage

If you've done all that I doubt it's the gasket. I've seen them seep but they usually have to sit for days before they'll drip. Still, the ribbed gasket TB specified is the way to go. My trans always seeped a little with every gasket I tried until I installed one of the ribbed ones. Took care of the problem completely. My guess is it's not your pan gasket but rather something else like Pishta said. With a new trans it's a little harder to tell when ATF is trailing down from something cause it's so clean and clear. What you need to do is get under there and clean every bit of ATF off with brake/carb cleaner and lay there and watch things for a while. May take laying there 1/2 hr or more but you'll eventually see where the fluid is escaping from