The tubes are only around 4 inches long. How would sticking out the other side show that you have a long penis? It might, but you could just as easily be below average. Also, if you can fit in the tube it probably means you are below average girth, which would usually, but not always, mean that you aren't particularly long.
I don't have any pictures of trying, I haven't done it in years, but I can't get the head of my cock inside. I also remember it being pretty painful as it dried out the head of my cock very quickly and caused a lot of friction. I feel like if you want to know if you're long or thick or neither, it makes a lot more sense to use a ruler or tape measure.
