How had you planned to power it?

"Think i can mount the fan directly to the T&G in a 4" octagon metal box without any other support to the T&G?"

Yes.

as for mounting it, thanks for clarifying... i just wanted to make sure it wouldnt fall down due to the 6 foot span...

as for wiring, i was going to use the flatest wiremold i could find and run it along the beam. and then the short run to the fan

keep the ideas coming

thanks

While the 2x will support the weight of the fan, you need the shallowest wiremold box for the connections, however, because the material gauge of the standard box is not sufficient to support the fan, you may need to modify it or purchase a box from an elec. supply house.

I plan on using a heavy duty metal box, approved for fan use (not a wiremold box), but use the wiremold to hide the romex for the majority of the run.

thanks!

You should also consider using individual conductors which will eliminate the crowding, overfill and stress in the 90 degree corners, that can be encountered with 14-3 romex.