I have an existing installation that has 6 inch deep metal studs and a vent pipe to the roof. Aligning a model 500 box to the dryer's vent location is a problem. The box's vent opening would be blocked by a gas pipe box. Moving the dryer box to the right to clear the obstruction would offset the box opening too far right from the dryer's vent.
It appears that I have three options. 1) Cover the existing hole and cut a new hole on the top at the right. However, due to the gas pipe obstruction and dryer location, the exact placement of the box leaves little tolerance, so I hope there is a better solution. 2) Cover the existing hole and cut one in the side and use an elbow. 3) Use an inverted model 4D box. The box is much better aligned with the wall vent and the dryer vent. However the left metal stud needs to be relocated to the left to allow the box to fit between studs. Its not clear to me if a horizontal frame is required to support the box at the top and/or bottom. Obviously, this option requires more effort.
Any suggestions you have would be appreciated.