You’ll likely be fine so long as your bag isn’t overstuffed. I occasionally travel with the Tumi continental and haven’t been hassled (ironically enough it’s the same one UA offered to its FAs despite it being oversized on UA).

The gate bag police were out in force at ORD on Wednesday and Friday. Anything being carried by folks in the main line that looked remotely oversized was being put in the sizer. One bag even fit, but it was checked as it had to be slightly pushed in.