I cant help ya with the GBC but I can tell ya bout the Smok GDC..
I modified mine ta make it get more airflow & kick like a mule...
This tank came stock with 2 holes in the ring & 4 graduatiing size hole in the base,,
she now has 4 bigg holes in the ring & 4 bigg holes in the base...
RedNeck with a cordless drill,, aint nuthin safe!!!
btw,, I can twist ring ta where a draw is like sucking gum through a straw or open it up ta draw like Aspire Atlantis... best of both werlds...