The caption says it was a 26 ft launch tube. I wonder, would you put the explosive at the very bottom, or in the middle? Packed right next to the firework, o

The caption says it was a 26 ft launch tube. I wonder, would you put the explosive at the very bottom, or in the middle? Packed right next to the firework, or some distance from it, for the gases to be able to act most effectively?