I’m installing a wood stove in a single story timber frame with a 16′ cathedral ceiling (there’s no ridge beam).  The 6″ stove pipe will run past a tie beam and I’m trying to determine the least obtrusive way to safely run the pipe past the beam. Double wall stove pipe would cut the required clearance down to 6″ and I’m wondering if  a piece of 24-gauge sheet metal, attached to the tie beam with 1″ standoffs to allow airflow behind it would allow me to go even closer, and if so, how much. 

Any helpful replies will be appreciated.