Is there any reason given either in the movie, or by any of its many analysts, why Abe and Aaron must make the 6 hour trip backwards themselves?
Could they not have designed an intelligent device, as discussed in this article, that would allow them to just send a piece of paper backwards in time at 2:30PM with the stock market information from the day, which they would have picked up at 8:30AM when they power up the machine?
Here's the relevant paragraph from the article I linked above:
Almost immediately once they discover this, Aaron and Abe reason that if they could create a device which had some degree of intelligence, like a programmable miniature robot or something, they could program the object to measure the amount of time that has passed and then spontaneously trigger the collapse of its own waveform from inside the box, thus selectively exiting the box at point B or point A. From this they imagine a box where the robot is inserted at 12:01pm, point B, waits for one minute, climbs out of the box at point A (12:00pm), and thereby travels backwards in time."