Long story short, I made the mistake of trying to save money on transborder shipping by ordering a custom frame (unavailable in Canada) for pickup. The store gave it to me in a shipping box which is 26x24.4x3.5in, which is much too large to carry on, but can be checked in if I'm willing to risk the frame/glass breaking. The frame itself is 19"x17" according to the manufacturer, so it's also a bit large to carry on. This poor planning has come to a head, and now I'm flying PHL-YUL-YEG tomorrow on a CRJ-200 and A223 - all in Y, in the exit window for both. Is it even worth trying to fit it under the seat in front of me, or is checking it in my only realistic option?