I have a new 2 story addition behind my garage. Above my garage is the master bedroom. The joists under my bedroom are 2x8. I need to move a supply duct over one bay that feeds my bedroom. Do you think it would be feasible to just use a 90 degree elbow to jump to the next bay or would I weaken the one joist too much putting a 6 inch hole in it. My ducts are 6 inch. Any other thoughts would be appreciated.