We had a chance to retest the 8″ Fuel Mine today. The previous test was only partially successful. We were using the 4 oz (liquid) PET bottle for a 5 oz (dry) charge and it barely fit. We determined we needed a little more lift and that meant the larger bottle and the higher holder in the bottom. We also decided to use a little more water to cover the charge by at least 1″.
With those changes made we created charges with 10% more powder (157 grams vs 142 grams) and set everything up. Water covering the charge by an inch, 4 gallons of gas, everyone in position, and hit the fire button. The results were perfect: