Do you need to enlarge/change the internal mechanics when you make hands as long as these? I don't really know anything about mechanical clocks; it just got me wondering, because it seems like there would be quite a bit more inertia/momentum to them. Regardless, it certainly looks awesome.
So far, as long as the hands are balanced the motor seems to be able to push them. If I leave the minute hand really thick in the back, and grind the long point down really thin, it should be just fine. I do however open up the motor casing, and replace the center pin with my own brass one. This gives me a more solid surface to attach the hand.