Originally Posted by Ben Piecuch

1) Why is the wheelbase so narrow? Even without any weight on the top, I can see this drivetrain constantly rocking back and forth onto the steep incline/decline sections.
2) Do the two, lower idler pulleys extend beyond the lower edge of the bottom, flat plate? If not, you'll have some excess friction on that plate, which will kill any efficiency you have. You'll need to lower the idlers, or put more idlers in the center of that plate.
3) Ah, now I see the tight wrap around the driven pulley and it's two idlers. I guess you'll have to read the specs on your specific belt.
4) Using a double motor gearbox, you should be able to gear that a little higher and still have the same pushing force. I would imagine that you'd still slip the belt on the carpet with a bit less torque...