That's a good point, the 4-brush brush roll he used actually has replacement red and orange strips which are more aggressive than when it normally has the softer black strips.
That's pretty baffling to me that you believe the 11 blade fan in a high performance motor doesn't run as well compared to the 6 blade fan, I've seen some collectors that perform airflow box testing that record the 11 blade fan draws more airflow than the 6 blade. I think it may be your hybrid 4 brush, brush roll that may have an influence on how it performs on the rug lift test.
