I'm trying to figure out how to install my Quadrafire 7100 and when I was looking closer as to where I would making the hole for the external combustion air intake, I discovered that the hole would be right at the intersection between the brick chase exterior side and the wall (for some reason, in my mind, I thought I could go straight out -not true). Take a look at the photo, it seems the centerline of the hole would be right at the intersection.

It's a tight fit and I really don't have room for flex tubing and relocate the intake.

I was wondering it would be possible to simply frame in a channel that will connect the inlet on the fireplace and the external air intake. I know return air on central air is done similar to this when they route the return air between two 2x4s 16" apart.