How I prefer to do it (and how we set up Omni builds with SRAM 1x mechanical) - keep the shift housing OUTSIDE the extension. Hide it under bar tape, then after it exits the bar tape, it has a nice gentle path down, around the Monopost, and into the cable inlet at the front of the Cable Cover part. Virtually no extra frontal area exposed to the wind, excellent functionality, and this option makes it really easy to make adjustments to stack and tilt without binding the cable. Personally I think it looks better than your other suggested option (out the back of the extension), but if you're planning to make EXTREME changes to stack and tilt over time, this option potentially makes it a little easier to do so.