Joe, that is a good story about the Coca Cola bottles. The first knee jerk reaction is always no way. But upon second thought, I would say that it could be a possibility with the right conditions. First all of the force would have to be straight down. Since it wasn't pulling anything or needing traction, I would think this could be accomplished. Second, I would hope there is a creeper gear or some very slow gear to "crawl" up also helping with the downward force. Third, you could argue the fact that having the axles at such an angle the lower wheel on the ground would be carrying more of the tractor weight than the wheel in the air. Therefore the bottles don't have to support a 1/4 of the weight of the tractor. Fourth, if all of the above is true, then one would need to know the static crush force of the glass bottle. The cylindrical design plus the "hour glass" shape in the middle of the bottle would only help the structural integrity of the bottle distribute the downward wheel force to the ground.
I am not going to bet my mechanical engineering degree on it, but I would say it could be possible under perfect conditions.
Joe, you bring your GP, I will bring the coke and we can settle this at the next show!!