As a general rule of thumb, the outlet should be about 75% of the fan area. Say you have a 5" fan, 5" x .75" = 3.75" for your outlet.

In most cases you will always benefit from ducting to the fan. Open it up as much as you can....the more air to your fan the beter!! Just roll 2oz cloth over some wax paper, and then brush or spread on the resin!!

Good Luck!!

Joey.