Harman DVC-500 Efficiency

I just completed my fourth burn test of the efficiency of the DVC-500. This test will compare the before and after results of the Modification I made to the firebrick and pot.

Before Modification
Burned 95# of Blaschak rice, bulk.
Stove Temp used. Set to 1 1/2.
Feed rate set to 1.
Stove Temp set to High.
stove burned, unattended, for 71 hours before going out.
BTU's produced was guesstimated at 10,000/hr. (based on the fact that the minimum setting for the DVC-500 is 7000 BTU/hr. I ran it 1/2 point above minimum.
Ash was 14#, with some bone and 'crustys'. Completely white ash.

After Modification
Burned 95# of Blaschak rice.
Stove Temp used. Set to 1 1/2.
Feed rate set to 1.
Stove Temp set to High.
stove burned, unattended, for 86 hours before going out.
BTU's produced was guesstimated at 10,000/hr. (based on the fact that the minimum setting for the DVC-500 is 7000 BTU/hr. I ran it 1/2 point above minimum.
Ash stayed the same at 14#, with some bone and 'crustys'. It appears to be a more efficient burn.
Completely white ash.

Conclusion:
Total burn time went from 71 hours before the modification, to 86 hours after the modification, a difference increase of 21% longer burn time.
Surprisingly, the ash wieght remained the same. I don't understand why, as there was not alot of unburned coal dropping into the ash pan.
I am VERY happy with the increase in burn time, but I may just repeat this test again, to verify the ash weight.