I'd definitely give it 24 hours. And you have the probe taped to the heat tape, correct? I have (counts....13 holes in the front, 8 down each of the sides). I don't currently have holes all around the tub, the 8 down the side are spaced about 2" apart so they don't go all the way back. This way the back stays warmer and the front cooler (an exaggerated heat gradient), but that's just my preference. And it allows me to flip tubs around and keep in more heat/air if need be, rather than a uni-directional tub.

I would recommend using a decent sized soldering iron. The tip of mine is 1/4" in diameter and seems to work perfectly.

Also...VENTILATION!

JonV