Adding additional ducting, why not got through existing walls?
Every time I read about someone who needs additional ducting the suggestion on the list is to go through an existing wall. Why is that?
My second floor master bedroom is woefully under-cooled and I can't help but think adding a supply would help. I know that my system would need to be recalculated for the load and that it also needs more returns. But why not look into going through the existing exterior walls for a few additional return? Dry wall repairs aren't fun but they aren't horribly expensive either. None of the HVAC professionals who've looked at our system have mentioned the possibility.
What am I missing that makes cutting out part of your wall to fix a major A/C issue the last thing on the list to try?