Stacking circles

Question

When I tried to stack 21 circles of radii $(30, 31, 32... 50)$ on top of each other in a tube (ID of $100$ wide), I thought they would reach the same height regardless of the order, however I was wrong. Here I tried out three different arrangements of what order to stack the circles, from largest to smallest, alternating largest and smallest, and alternating from middle to largest and working smaller. I cannot come to a clear conclusion of which way would stack all of the circles in the lowest height. Does anyone have any idea of what method of stacking would give the lowest height?