I'm stumped on what I thought was a relatively simple thing. I need to make a see-through fireplace and can't figure out how to get everything to cut the related walls correctly. What I'm trying to get is to have the fireplace unit cut the studs in the wall but not the GWB, except at the see-through firebox. The unit (Napoleon Vector™ 50 - LV50 2) has a big rough opening that the drywall will cover and a smaller firebox.

The studs are 16.75" out-to-out which is too far away to join the walls and I can't figure out the correct combination of openings & voids to get everything to cut properly...